IMHO, There's no magic in having the first channel so build a lite version. Even leave out the Tremolo and use a pedal if/when you feel the need - no magic there either to the circuit and tone. But build everything remaining as it should be and be where you want with the least amount of hassle. I am also convinced that part of the magic of the amp's tone is the cabinet size. I would keep this as close as possible to spec. I would use the extra interior space to improve the layout, grounding, and lead dress shortcomings. I will say at my last outdoor gig playing alongside my bandmate's vintage '65 BFDR I had guys come up mid set complementing my tone over that. But it must've been because I used my custom 6v6 jcm/plexi mounted with a Scumback paper voice coil? It's a serious tone machine and waaay more versatile than a simple DR...
If I am building a Deluxe Reverb Blackface and do want to have the 2 channels, I still prefer to use a different chassis that has a mid control. It is fairly easy to have a 2 channel amp the old school way and use a A/B pedal, but for Studio Amps, noise is the biggest problem.
My problem is I think of too many things I need more pots for. I just finished an amp this weekend that started out as a AB763 Deluxe Reverb, but now it is a 1 channel amp with a custom faceplate and 2, 10"s ousted of 1, 12. I started this for a friend who "said" he wanted a "exact" 65 Deluxe, what 65 has to do with this, I really do not know.
He was over and we were discussing the build and he has never played any of my amps. Well I got a Deluxe with tons of mods like the ability to have a plate driven tone stack or CF stack, Raw, additional gain stage with switching Plate Resistors and Bypass caps with the next tube being s cold clipper. Everything is manual as I built it before I began using 5 volt switching. All the preamp tubes run DC. Adjustable NFB, 2 master volumes, Pentode/Triode, you know all the junk.
It will do the perfect stock Deluxe Reverb AB763, but much more and I prefer the tone of 6V6 when in the CF mode, just sounds more Marshally whereas 6L6 Tubes don't get there.
And no, I do not think it is a good idea to build for sale amps, even though I do sell ones I am tired of, however money can be made on repairs and mods. Well, after playing around with mine he decided to add some mods and when I installed a set of Tung-Sol 5881 stock went out the window.
Of course I was a little restricted with the smaller chassis, but was able to give him the mods I use often. Tweaking the amp cost him more in labor than building the whole amp. Herein lies the problem when we build. We don't have to think of a market price point or are we building an amp that hurts another amps in the lineup value.