It is possible and something I have played with in script form (in the test, I "deployed bipod" on an M4 to make a M249; Just a proof-of-concept until I find someone who's made a bipod-folded and bipod-extended version of the support guns ;P). I was also trying to allow bracing of weapons to stop fortifications being death-traps, since when inside a fortification or behind sandbags, although you are a smaller target, you aren't really smaller than someone who is prone, but your accuracy is for crouching or standing, so the prone man outside actually has the advantage).
As far as I can tell, the way you'd do this would be to replace the bipod-folded version with a bipod-extended version that had less recoil (you might alternatively increase the prone recoil for the un-bipodded weapon, since I assume the values assume bipod deployment). OK, seems simple so far, but there are a multitude of problems:
* What if the player stands up? OK, when that happens I force the player to lie down again; you could alternatively disable crouch/prone buttons. Alternatively, just unbipod any weapon in inventory every second if you aren't prone, which also deals with the dropping and death problems (see below).
* What if the player crawls away or rotates with the bipod down? You could stop the player moving, or assume that the bipod wouldn't get in the way.
* Whenever you replace a weapon object in this way, it is automatically reloaded. Unavoidable, but I can live with it.
* What if the player drops the bipod weapon? Easy: disable gear menu; Harder: check ground and containers nearby and un-bipod any dropped guns.
* What if the player dies with a bipodded weapon? Replace weapon in killed handler.
Another question is, do you want it to only be usable by players, or by AI too.
Overall, I don't think prone bipods are that important (compared to crouch/standing bracing of weapons). You already get a huge reduction in recoil with MGs when prone, so the game is already assuming you are using a bipod. You'd only be adding a time delay for use of the bipod and making it highly unaccurate if you didn't spend a few seconds deploying the bipod (how long does it actually take, anyone who's used one?). Still, I think a system for bipods and bracing would be very nice to have.