Nice write-up.
Although, you could just buy one of the many VW specific units available out there, cheap and nasty for $300ish and higher quality units around the $600 mark, like the Audiosources units on this forum, or Dynavin etc. At the more expensive end ($1,600ish approaching $2k) even Alpine and Pioneer have VW specific CAN-Bus compatible units. With all of these just remove original unit, plug in new unit, replace trim, done.
Speaking for my own Audiosources ANS-810, it has 8" screen, proper line-level outs, video out for rear LCDs, video in, aux audio in, reverse camera in etc, plus Full (or nearly) CAN-Bus functions like MFD display and door open status, OPS parking display etc + full steering wheel controls. Other brands may do similar things. So many VW specific options, I would never consider generic Alpine / Pioneer units. Just saying :wink: