The Sig P320 can't pass a drop test is the issue with it. I don't think anyone is bothering to home build them. There's a plethora of other options for making your own in a variety of ways on the Glock platform alone.
I've been in the home gun build community for years -pretty well have my finger on the pulse of this one. The Sig drop is a cliched joke at this point, and nobody cares about building one. 3D printing has already made gun control obsolete as well, and if anyone wanted a Sig anything, they would have one.