What I really don't want in a mech game is the typical japanese style mech with human proportionate body profile and hands with which it can hold huge weapons that have same ergonomics as human firearms, but just bigger. I am talking about mecha from anime like evangelion, rahxephon or god forbid the rollerskating Code Geass mechs.
I want mech to look like they are designed for practicality, not aesthetics. This is probably why I never liked Atlas mech, it looks too much like a humanoid to me. Also I think it is important to have somewhat realistic movement on mechs, so as I mentioned before, no damned rollerskating mechs aka code geass.