Just a thought following earlier pondering, apart from the 20mm axle being a bit of a PITA I’m generally fine with the old 150 Revs I’ve got for my 26er.
Rather than go hunting for a whole pair of forks and starting again from an unknown point with whatever I find when opening them, am I right that I could just get some with knackered CSU etc and swap the lowers to get a 15mm axle? I think that way the bushes of the ‘new’ lowers would be all I needed to worry about over a standard lowers service?
it definitely isn't compatible between argyles and sectors - I tried it myself (for the opposite reason to you) and the bottom of the fork leg is lower on one of them (can't remember which off the top of my head) so the cartridge/spring length was all wrong.
I would assume the same of revs and whatever else. FWIW I think the 20mm maxel is much better than the 15mm one which appears to be made of cheese, so stick with what you've got