High gain amps are indeed an order of magnitude more difficult and notoriously difficult to trouble-shoot; this is particularly true if you want something the involves channel switching; that's probably why you don't see any kits out there. Most of the truly high gain amps (JCM900's, Dual Rectifiers, etc.) are all PCB-based amps b/c a hand-wired version of these types of amps would be a nightmare to wire and would be very prone to all kinds of noise and oscillation problems.
The other reason is that there's probably more of a market for vintage Fender type amps than anything else.
The AX84 November is probably a good choice for a simple, high gain project.