Technically, any arsenal reworked M4 or M16 is a "franken-gun"...
You don't honestly think Anniston segregates Colt bolts and bolt carriers, etc, from the FN ones, from the replacement contract ones from third sources; and then meticulously puts them back together with matching parts?
As long as your stock of parts is quality, the aggregate of those parts will be quality...(assuming there is quality in the assembly work).
Who supplies "quality" parts is another debate entirely.