I have been throwing around some interesting ideas with the other 2 non-dev members of my team and getting their feedback.
So far here is the list we have come up with:
Upgradeable HEV Suit:
On certain objectives (secondary and special) you will have an opportunity to collect parts from completing them. These parts can be traded in at terminals found throughout the game to upgrade your HEV suit.
Upgrades would include slight armor increases, max hp and power increases in increments of 5 points.
At these terminals you can also tweak your weapons with parts. You can increase the damage slightly or increase the max amount of primary or secondary ammo that the weapons can hold, and increase the clip size.
granted these are just ideas, I am no where near sure where to begin to accomplish these but from ideas come life so I am sure that applies to coding somehow.