I took the question to mean for what purpose will the weapon be used. Maybe I'm wrong. Wouldn't be the first time.
Primarily, it was to gain knowledge of the gun but it was also enjoyable. Also, I got a very high quality rifle for much less if an investment.
I would have, but it is a felony here in Australia unfortunately. Nothing a good trip to the states can't fix
Not a full build but I have taken several PSA or Spikes complete lowers and put CMC, Timney, or Hiperfire triggers in them and pair them with PSA upper and a Geissele or Radian charging handle. One of my friends, whose daughter I coach in several shooting sports, shoots steel with me. I built a 9mm steel gun for him using a CMC Trigger, PSA uppers and lowers, Geissele charging handle, and a C-More railway sight.