Well, it's a much better idea than modding a Beretta carbine to take Glock mags. My suggestion, buy the HiPoint 9, take it apart, see what can be done. The worst case, you end up w/ a reliable, accurate 9mm carbine that the cognoscenti laugh @ until you outshoot them. The best case, we end up w/ much better stock options than we have now - A, the old HiPoint stock, B, the new HiPoint stock w/ plastic rails, & C, the Beretta lookalike stock. And no one's ever going to use Glock mags in a HiPoint if someone doesn't try. You're the guy.
I'm trying to remember from when I swapped from the old to the new factory stock, but I think you'll have to remove some metal from the frame below the bolt to fit the Glock mag in there. What I don't remember is if you'd have to redo the trigger bow.
Even if you could figure out how to make it take 1911 mags, you'd still be a hero.