I can see your point
Which inspires the idea - one frame and over time you can train/buy modules. The modules the determine weapons and other "class" related equipment that can be placed on the chassis.
Classless systems work well for single player, but every MMO I have played once the Meta is determined that pretty much all you will see.
However a broad overarching skills that could be applied to multiple frames could be viable. Eve online has something similar.
One aspect that I believe needs to be addressed (although it maybe slightly tangential) is the f2p breeds griefers.
Along with playing Firefall, I have been a long time player of Planetside 1 & 2. A trait that is common among FPS games is the extremely competitive nature often results players...