A few pounds of PLA later, the enclosure wasn't feeling very warm & fuzzy.  Like the days when lions built H bridges from scratch, there's probably an off the shelf enclosure for a reasonable price.  It seemed to need a 2nd layer of coroplast.  It wasn't clear how reworkable it would be.  Connections would have to use screw terminals wherever provided.  A battery connector would connect the inverter + control board to the Meanwell.  Then it could be powered from the bench for testing.

The inverter + control board + relays would have to be 1 unit because of the large number of connections.  The fan would need a connector, possibly going straight into the meanwell.  Some empty space was provided for the fan to blow into.  The fan would run continuously, since the relays get hot. 

Started pivoting back to 10 voltage steps with 10 being bypass, since battery power is never going to be used.  Nowadays, it's more common to have 12V DC fans for off grid use.