>>237557
>>237578
Some options for all three, with parts and mags commonality in mind
Raw practicality over form factor: AAP optionally with a stock, uses TM-spec Glock mags, is cheap, plenty of external and internal aftermarket to fuck with, also plenty of printed shit if you want to do anything from pretend you have a real submachinegun to making the externals necessary to run a gun from Halo
A practical gun that looks a lot more normal: TM-spec Glock, also with the option of a stock or perhaps a low-profile carbine kit (ex. USW), also (obviously) uses TM-spec Glock mags and has plenty of aftermarket to fuck with
There's also a few routes into an FMG9 if you want a compact SMG using TM Glock internals and mags, but they're expensive and/or not clear on whether or not they're any good - easiest route I can think of is that Poseidon and Acetech recently collaborated to produce a plug-and-play FMG9 that doesn't require a donor gun and comes with an integral tracer unit, but I don't know enough about Poseidon to judge whether or not their Glocks are any good so probably look up some reviews and ask around before pulling the trigger, and after that you'd still benefit heavily from buying some real irons or a red dot since the FMG carryhandle has some very low-profile, short sights in it