Well that's just a 3D CAD drawing (and is a LOT smaller on Armalite's site! Whoops...). It's certainly less bulky than an ARMS #58 I think. Furthermore, I don't have the $3000 to drop on an M203 so that's not a great concern for me either. I was considering the #58 for a while and was in fact why I chose a midlength upper, but after seeing its relative size I started to look for something smaller (I also didn't want to start taking stuff apart). The Knight's RAS series would be perfect but they don't make one in a midlength config. Looks like Armalite's product should fit the bill.
On a related interesting note, M203 40mm grenade launchers are unrestricted items in Canada. You can buy one across the counter, no paperwork needed, because they fall outside the legal definition of a firearm (muzzle velocity <500 fps). [:D]