Short answer is, you need an integrated air data computer to be BaroVnav capable. Your Garmin 430W can fly SBAS VNAV which is currently under trial and hopefully rolled out in a few yrs.
So SBAS supports most light end GA and BaroVNAV supports the higher end market. I dont think S340's are capable and only Proline Kingair. Your arguments around Baro are relevant. Baro does nothing for most of GA and wouldn't have prevented YLHR.