DPMS is on the low end of acceptable for ARs.
And you can also do “no paperwork” with a private buy of a lower.
An 80% receiver requires about $300 in tooling and jigs to complete. Which means it costs more than finding a lower from a private seller.
Tooling isn't a problem... (hehe)
Probably the only things I'd need to get is a clamping block set, and possibly a tap.
http://www.cncguns.com/tooling.html (tool/tips/resources)
The only reason I mention DPMS is because they are the only people I am aware of that make a 7.62x39 ar-15 barrel.
If I knew of someone who had an ar-15 lower that they wanted to unload, I wouldn't mind going that route. (If it was in serviceable condition.)
Really the issue is the upper and all the internals.