It depends on how clever you are and how adaptive you can be
The KMX boom is a square boom , the position of the changer mech needs to be in the right place ( check the position on a df with respect to the chain angle
A couple of flat plates could be bolted just behind the bottom bracket shell and with a bit of clever-ness you could make a bolt on plate
or remove the BB assemble and get someone to mig/tig a tube onto the BB I believe the boom on that KMX is steel .
Atomic zombie is the website where most trike builders are found including me ,
FYI DNP make a freewheel unit that goes down to 11t but 44-11 is only a 80" top gear