Cutting right to the chase… this is what needs to happen (In my opinion, not yours) to have a sort of balance in Supermechs.
Tldr; covers Items, SM currency/Tokens, EXP, PVP (Clans also), and a bunch of other features
Starting off with items:
 Increase max Item limit to 150 items at level 0 with 15 item slots unlocked every 3 levels. You would have the option to purchase 15 additional slots at the cost of 25 Tokens or 75,000 SM with a 5 Token & 15,000 SM increase with each purchase. Maximum of 1,100 Item slots (max level player has 150 + 750 item slots)
 Redo box opening… rates, prices, more boxes, etc…

Silver Box stats:
Price: 3,400 SM, price increases with each box purchased by 250 SM for first 10 boxes opened. After the first 10 boxes are opened the price increases by 750 each box. Price caps at 35,000 SM, price resets daily or you can pay 35 Tokens for a price reset once a day.
Rates: 50% Common, 46% Rare, 4% Epic, 1% Legendary with 100% chance for 2 items and 50% chance for an additional third item or Powerkit (max tier Rare for Powerkit).

Silver Box stats:

New Gold Box stats:
Price: 15,000 SM or 15 Tokens, price increases with each box purchased by 1,000 SM and 1 Tokens for first 5 boxes opened. After the first 5 boxes are opened the prices increases by 3,000 SM and 3 Tokens each box. Price caps at 125,000 SM and 125 tokens, price resets every 36 hours or you can pay 125 Tokens for a price reset once every 36 hours.
Rates: 20% Common, 60% Rare, 16% Epic, 4% Legendary with 100% chance for 3 items and 60% chance for an additional fourth item or Powerkit (max tier Epic for Powerkit). 
Premium/Mythical box stats:
Price: 100,000 SM or 100 Tokens, price does Not increase for the first 3 boxes purchased. After the first 3 boxes are opened the price increases by 10,000 SM and 10 Tokens each box. Price caps at 250,000 SM and 250 tokens, price resets every 48 hours or you can pay 150 Tokens for a price reset once every 48 hours.
Rates: 0% Common, 0% Rare, 90% Epic, 10% Legendary with 100% chance for 4 items and 80% chance for an additional fifth item or Powerkit (max tier Legendary for Powerkit).
Note: Keep in mind that each item in a premium box has a 10% chance to be a legendary hence the price increase.  Globally redo item drop formulas in campaign, each item will have its own chance to drop. Different tiers of items can drop per mission and those separate tiers can drop more than one item.
 Common Items: 30% (base drop rate) + 3% x 1~8 (campaign area you are doing) x 1.00/1.30/1.60 (Normal, Hard, Insane) x 1.00/1.30 (1.00x if normal account, 1.30x if you have premium).
For Multiple Common Items: each successional Common item dropped after the first has 1/5 less of a chance to drop. Max of 5 Common items per mission. Rare Items: 20% + 2.5% x 1~8 x 1.00/1.30/1.60 x1.00/1.30
For Multiple Rare Items: each successional Rare item dropped after the first has 1/4 less of a chance to drop. Max of 4 Rare items per mission.
 Rare Items: 20% + 2.5% x 1~8 x 1.00/1.30/1.60 x1.00/1.30
 Epic Items: 10% + 2% x 4~8 (only obtainable past area 4) x 1.00/1.40/1.70 x 1.00/1.40 + .2% x player level (max of 97.88% chance with lvl 150)
For Multiple Epic Items: each successional Epic item dropped after the first has 1/3 less of a chance to drop. Max of 3 Rare items per mission.  Legendary Items: 1% + .2% x 7~8 x 1.00/1.30/1.60 x 1.00/1.30 + .04% x player level (max of 11.408% chance with lvl 150)
For Multiple Legendary Items (GL): each successional Legendary item dropped after the first has 1/2 less of a chance to drop. Max of 2 Legendary items per mission.  Buff weekly clan tournament item reward to 5x 5,000 Powerkits with no fusion cost and a legendary item or a single legendary item of the guild’s choosing but no powerkits. (This needs some work)
 Changes to PVP item drops:
 100% chance for a item box to drop if you win your first battle of the day (drop rates are equal to a silver box).
 Every second win, fourth quit, or fifth loss, you have a 85%/60%/45% chance for item box to Drop on par with a silver box.
 If you manage to achieve a win streak you gain a bonus box with boosted drop rates for every 5 wins in a row (quits do not reset the streak). The box is on par with a Gold box with +6% chance for a epic, +2% chance for a legendary.
 Item boxes upon leveling up
 Level 1~5: 2x Silver boxes
 Level 6~15: 5x Silver boxes
 Level 16~25: 8x Silver boxes, 1x Gold Box
 Level 26~35 10x Silver boxes, 3x Gold Boxes
 Level 36~45 12x Silver boxes, 5x Gold Boxes, 1 Premium Box
Etc…
Onto SM currency/Tokens changes:
 Increase level up rewards:
 Formula for SM gain: 2,500 x 1~150 (player level) x .05 (per completed achievements) x.05 (per completed campaign areas, only counts on normal)
 Formula for Token gain: 10 x 1~150 x .025 x .025
 Increase campaign SM yield:
 New formula for SM per mission: 500 (base SM) x 1~8 (area you are doing) + 100 SM per mission number (example: The Dry Lands mission 3 is worth + 300 SM) x 1.50x (if it is a side mission) x 1.50x (if it is a boss level) x 1.00/1.25/1.75 (Normal, Hard, Insane) x 1.00/1.50 (Normal account is 1.00x, premium account has 1.50x) x 2.00 (only on first clear)
 Redo PVP and Clan ranking:
Starting with PVP, this would be the new formula for PVP SM rewards:  If you win: 2,500 SM x 3.00 (If first within first 5 battles) x 0~X (X is the rank difference between you and your opponent, +1,000 SM per rank with no penalty for being a higher rank than your opponent) x 0~X (X is the level difference, +100 SM per level less than your opponent with no penalty for being a higher level than your opponent) x 1.00/1.50 (Normal account gets 1.00x, Premium accounts gets 1.50x)  / + weapon level difference (10 SM per 1 weapon level you have over your opponent or +20 SM per 1 weapon level your opponent has over you)
 If you lose: 500 x 3.00 x (0~X, minus 1,000 SM only if this amount is greater than 2,000 SM prededuction) x (0~X, minus 2,000 SM only if this amount is greater than 4,000 SM prededuction) x 1.00/1.50 (Normal or Premium accounts)  / + weapon level difference (50 SM per 1 weapon level you have over your opponent or +10 SM per 1 weapon level your opponent has over you)
 If you or your opponent quits: 100 SM x HP remaining flipped (meaning if you or your opponent has 30% HP remaining it is 100 x 70 SM for both sides). If either you or your opponent has over 75% HP, no rewards are given to either side.
 Next is relatively short, Clan rankings
 Main rewards are given to the top 10 guilds, if ranked in 100th or better, 25,000 SM, 25 Tokens & 5x Silver boxes are awarded.
Ranks 108: 100,000 SM, 100 Tokens, 3 Gold Boxes, 1x 10k Powerkit & 3x Epic Item
Ranks 76: 150,000 SM, 150 Tokens, 5 Gold Boxes, 2x 10k Powerkits & 5x Epic Items
Rank 5: 200,000 SM, 200 Tokens, 5 Gold Boxes, 1x Premium Box, 3x 10k Powerkits & 1x Legendary item
Rank 4: 250,000 SM, 250 Tokens, 7 Gold Boxes, 3x Premium Boxes, 4x 10k Powerkits & 1x Legendary item
Rank 3: 300,000 SM, 300 Tokens, 7 Gold Boxes, 5x Premium Boxes, 5x 10k Powerkits & 1x Legendary item
Rank 2: 350,000 SM, 350 Tokens, 10 Gold Boxes, 7x Premium Boxes, 6x 10k Powerkits & 1x Legendary item
Rank 1: 400,000 SM, 400 Tokens, 12 Gold Boxes, 10x Premium Boxes, 5x 25k Powerkits & 1x Legendary item
Next comes EXP:
 New EXP level requirements:
 EXP required for next level formula: 200 (Base EXP Req.) x X (X is your current level) + 5% (for each level you have had, example: lvl 11 = 50%)
 Increase EXP gained from Campaign and PVP:
Starting with Campaign EXP:  EXP gained from Campaign missions formula: 100 (Base EXP gained) + 25 (Per mission number, explained above in items section) x 1~8 (Campaign area, also explained) x 1.00/1.25/1.50 (Normal, Hard, Insane), x 2.00 (If it is a boss mission), x 1.50 (If it is a side mission), x 1.00/1.25 (Normal account gets 1.00x Premium account gets 1.25x) x 2.00 (first clear only)
 Next is the PVP EXP formula (pretty simple): 500 x 3.00 (On win and If within first 5 wins) x 2.00/1.00/.75 (Win, Lose, Quit) x 1.00/1.50 (Normal account VS Premium)
Now that those are out of the way I can move on to a few side topics:
 Token/SM purchasing is up first…Currently with fusion/item box prices as is it is not worth it to me to purchase Tokens to then buy SM currency at 1,000 Tokens for 1.5M SM. While this amount is pretty large it only lasts for about 15 minutes with heavy fusing and item box opening. The actual amount achieved with 1.5M SM starting from scratch is most likely a couple (2~4) fully fused Legendary items with luck… Compared with the fact at top levels you need a fully fused mech to compete now it’s either go for broke or nothing. Something needs to be done.
 Premium accounts, these guys need a buff to get your full “premium experience” up to speed. I recommend the following: +25%/50% EXP gained (Campaign and PVP), +20% HP in Campaign, No Ads, +50% SM gained (global), faster fuel recovery & and boosted Item drop rates (30%~40%).
 Fuel in Campaign, this is okay with a slight buff. Having the following rate for Fuel increase would be my suggestion: 20 (Base Fuel), + 1 Max Fuel every level up, + 3 Max Fuel every third level up. Fuel recovers every 5 minutes with a normal account of every 2.5 minutes with a premium account. You can fully refill your Fuel count thrice a day for 20 Tokens, extra fuel left stacks.
I think that covers most of what I wanted to say, I’ll leave my Salvaging idea for next time…
I wrote this entire thing on a whim (and I was bored) so there is almost 100% going to be a mistake or two somewhere…
Enjoy and review please. Leave feedback if you care, leave if you don’t