Feel free to disagree with any of the ideas here, but at least attempt (or fake) being civil.
1) Maybe let the alternate/prestige weapons be tested out, at least in some sort of training mode. Kinda like God Hand for the PS2, there was a training area where you could get moves and test them out before buying them. Likewise for here, allow the use of all weapons in the training mode so it's the user will know how a weapon acts first hand with the mech they are using.
2) Customizable garage area. A small area where you have something like the older training area that allows you to walk around, see your mechs (up to a point) and allow minor customization of the layout of the area. Perhaps even make it a MC only thing if you want (the customizable area itself, not so much the customization options). As a private area this garage would have fewer players allowed in (1-3 others) and they would have enough room to mess around or duel or whatever. A place in Hawken to kinda chill and give the Hawken experience a bit more of a personal touch. Not only that, it could add to some stage variety if the customizations are good enough.
3) Parking Garage type Level. Not entirely in a Parking Garage (that wouldn't be entirely intact), but something with multiple layers with a couple ways through them. An area that is less "slow, methodical combat" and a bit more "tense skirmish" or something. That said, outside the Parking Garage would be available as well.
4) In part similar to my garage area, a customizable area held by a Clan leader (once said Clan gets X amount of people in it. Maybe 8-15). Clan wins will give the Clan points to build upon the Clan area, and battles can take place within these area. Of course they won't be as intricate as the normal stages but it might add a bit of variety.
5) Maybe a jump button? An actual jump function? Nah I'm sure this will get shot down no matter what I say.