Nope, not gonna build one.
Have a buddy who lives in Brooklyn, New York, makes custom knives and scales and wants to make grip panels.
No way he's going to the trouble to get any kind of firearm license, but I was thinking an unfinished frame is not a firearm per ATF and even in NYC if there's no rails cut and he doesn't own a barrel or slide I can't find a statute that would apply.
So, basically a non-serialized frame with proper grip holes/bushings and maybe the mag release and plunger tub in place. Whatever holes that impinge on the grips that would keep it a non-firearm would be handy for fitting. Heck it doesn't need any top end above the plunger tube for that matter, no rail material at all.
I can't find any mentions online newer than 2009 or so, so I'm wondering if the ATF changed their mind about them?