what about two players with different classes (or same) can interact together. like a gren and an engineer who build a rocket turret (the gren has so sacrifice his launcher for this) so u can use this turret for shooting rockets @ a higher rate. or a rifleman and an engineer who build a sandbag barrier with a bipod hmg for extra stationary firepower!
the option the have a context sensitive "class-specific structure" is interesting, like walk up to rifleman, it says "press "x" to build "mg nest" which would be a few sandbahs that the engi can then build with his engi tool, maby have a lvl 2 that takes longer to build. Also, both the engi and the other person need to agree. Though how to ballance this is beyond me...
Ok, so the rifleman with no cover can magicly deflect bullets? Ya i didnt think so... Lets face it, theres not much cover on most maps right now, and i dont forsee much in the future, so being able to construct cover in the field (and walls dont work as well as most would like) would be VERY useful, and cant really be exploited, its a pile of sandbags you build with the engi-tool... if you can exploit that somehow then you have to be hacking or the map is poorly designed.