If you make it take Glock 19 and 17 mags and price it under 400, I will buy one and many others will too!
AP
ETA: The Kel-tec sub2000 is the only other carbine out there to my knowledge that markets itself as a companion carbine for the pistols you already have. If you make it take lots of kinds of magazines, I have a feeling people will get them so they can save the hassle of buying new mags. Sharing mags is also a big plus among the minimalist and survivalist crowds! Especially since I have to own 10-20 mags for every gun I own, lugging those things around is no easy task AND they become a small fortune once you have more than two platforms to provide mags for..
The Kel-tec sub2k is ugly as hell, your bullpup design is very nice looking (this coming from an AK person, so it doesn't mean much). Bullpup is a big plus over the sub2k--give us some good irons to boot and it'll be a seller. Perfect truck gun imho. Oh and one more thing, I'd like to see a decent profile barrel--no pencil barrel crap!
AP
ETA again: I like your initial design too--looks very mean. except for the top feeding concept how do you shoulder that? Again this is coming from an AK fan--many will disagree with me.