Beating the campaign from getting so many keys and beating so many levels isn't exactly worth it in my opinion, it would cost much less to just buy a bunch of gold item boxes. I think there should be special mech parts that can only be obtained from beating the campaign. Maybe they would have a special logo or something. These are just some examples


Ender:
4 phys drain
60-125 dmg
3 range


Ice Blade:
65-150
-20 heat dmg (cools enemy)
1 knockback
1 range