So... normally the recoil penalty on some heavy weapons makes their use (without massive accessories and whatnot) implausible, at least in open areas.

In confined areas, one could conceivably still inflict damage with such a weapon, if only because the bullets ricocheted (speeling) off the walls...

I guess I'm just moping about the enhanced damage of grenades in (relatively) tight spaces, while firearms are well... not considered.

eh, maybe. most heavy weapons would blow right through any normal interior wall. 'sides, autofire isn't hard to aim if you're using it the way it's intended to be used--3 to 5 round bursts. if you're trying to unload ten rounds into a different target, two or three times a second, you deserve to miss.

Well, the GM could give the opposite of cover modifiers. That would represent that the walls, ceiling, and floor actually increase the odds of hitting your opponent. That seems fair to me.

Flechette or buckshot seem especially heinous to me.

Or you could just use suppression fire over the small area and try to hit anything that moves in it. May not be exactly what youre thinking but this being a game and all theres at least one mechanic that comes darn close.

if i had my druthers, dodging would have a success threshold. in an enclosed area, like a hallway, your threshold would be 1 (you need 1 success before your other successes start counting); in a very restricted spot, like a closet, the threshold would be 2 or more. since that's a lot of bookkeeping to worry about, i generally just hike the TN one or two points instead.