The day has come!
Tested, working, and good to go. The only minor issue is that the G3 modem connectors I ordered are shorter than the last one I bought, despite being the "exact same" part from Digikey, so the fit in the G3 is rather snug. Luckily the connector still sits well enough for the board to work.
N.B. Versions being sold will feature either the G3 or G4 connector, not both (unless specially requested).
All that is left is for the parts for the G3 breakout to show up and then I'll start assembling these en masse and getting them shipped out.
Bonus:
Red or purple? You decide!
I'll send out messages to folks on the waiting list once things are ship shape.