Simon, you're nothing if not generous and thorough. Thanks for all the time and thought you've given this. I should clarify a few things though:
The "kit" amp is a printed circuit board and a handful of components that plug into it. That's it.The chassis comes separate, if at all. The pots and inputs etc for the "front" and the "back" are perforated and separate out from the main PCB but remain connected by wires. In theory you could set this up in any format you wanted to. I included the pic of the head version to give you an idea of what some folks have done with the kit.
I imagine when I remove the amp section from the Kustom combo, the back panel will be coming with it and possibly not getting put back on. I'm not sure at this point. The dimensions of the chassis and possible back panel are still entirely hypothetical.
That's EXACTLY what I want!!
I wanted the combination of tone/wattage/features this kit offers and can't seem to find it anywhere else. I like the idea of smuggling an amp like that in a small, neat, unassuming combo. Most importantly I want to own and play through this thing, and get there on the cheap. This means some assembly is unfortunately required. If I had to learn electronics from scratch and build a cab from scratch I don't think I'd bother.