I thnk that these two ideas could be a lot of fun for the game, and I do not think they have been suggested before (maybe in a much earlier post)
1. Allies
For an updated story mode, or as an upgrade itself, I think adding allies to the game could be very interesting. Of course, enemy armies would have to be sizable as the player him/herself already does tons of damage to enemy robots. The allied robots could be the same color as the player, and would probably be low-tier combat robots (the AI targeting system might have to be redone, as the enemies right will just track their single target, and multiple targets may confuse them). I just think charging out as a human robot with multiple allies on your side sprinting towards the enemy with you would be awesome.
2. Dodges/Rolls
When you or an enemy gets knocked down due to pesky spider grenades, you can roll to one side or the other. I think hat this feature should be an upgrade as well, at the cost of maybe half of an energy bar. This could be very useful to escape mk 3 hammer swings, and would allow the player to have more mobility.