Brilliant idea oh holy CorgiMaster, truly brilliant. Why the hell didn't I think of this?!
I think 35 days is perfect, the rewards are also pretty fair. A few tweaks I would make though.
1. Only allow 2 of any weapon on your mech, because it would just be mechs with Galaxsus Model B, 4 Death punches, all Rocket modules, and 4 Rocket kits with your rules
2. No kits can be used.
3. No healing drones allowed.
4. 50 health is gained after an enemy mech is destroyed.
5. Make it have a SM cost as well, because 5 battle credits is too easy to come by. Like 5000 SM and 5 Battle Credits, just so there isn't an instant an SM gain by beating 1 campaign mech.
I voted yes, I suggest everyone do the same.