I know exactly what your example meant, but comparing precision computerised machining to soldering wires isn't exactly like for like. (maybe if we were talking about computerised soldering of PCBs, but we aren't.)
I'm just cautious about giving someone who's obviously trying to get a feel for a market the impression that there's money to be made, have them make the investment and then find there's naff all in it or it requires so much faff (the variations, etc) it's not worth it.
even small changes like flipping it over to a front facing plenum need the AAC wires extending and if you were buying a loom, I'd want that accommodated.
there's 40 people confirmed on the RB swap register - if you assume that there's another 40 that aren't part of the SXOC, that's around 80 people in 4 years that have done them.
with your market being that limited, you'd have to be sure they've got the money to buy a decent product - but as you say, when you can get a loom adapted for £70-100, most people wouldn't bother.