Originally Posted by
Antifriction
Since you mention new hubs & drivetrain, you might consider a wide-range 1x instead of front shifter. Microshift Advent 9-speed (11-46t) is a well-reviewed budget MTB drivetrain. It's offered on some kids' 20" bikes, so ground clearance must be somewhat viable.
I couldn't fit bigger the 36T with Altus derailleur on one of my 20" and on another, 34T with medium sora was the max. Long cage derailleur would just about fit but I would have the tyre thickness as clearance from the ground. Not great on gravel path or fast right hand corners.