The V, JP & VII have big iron, and it doesn't matter. That's because it doesn't matter! The best pure tone from any II or III is with the 60 and it has small iron with PV in the high 400s. Go figure.
Hey now, I owned the VII for 6 days... Of all the "reissue" tones they've done in the V, JP & VII I think the one that's the most raw is the IIB tone on the VII. Not that it matches any IIB I've had, but it's the most raw.
The mode IIB sounds like a wraith of the original on the clip. The B is so fat it darkens it up but that could be eq'd on the mic. I like the dark but would dial the bass back a little myself.
So I say iron does matter and you can't compare any Mark II circuit wise with anything past the IV and for me it goes back to the day we played all those amps in your garage. I know you had the JP and can't remember if you had a V there. I think I unconsciously that day decided I didn't care about any Mark past the IVA with the ampeg looking grill I had up there.
The obvious was how the compression/clipping progressed from the B coli, B 60W loop mod, III's (blue coli and green) to the JP. I've long had the theory that the more components you cram in a box the more you are trading off.
The 1st part of that is capacitors. All filters use capacitors and there is a frequency roll off. I may be just smoking too much (ha, as if there is such a thing) but when you look at a 60's Fender or Marshall you don't see a bazillion caps crammed in there, a result of multi-channels bells and whistles.
The re-issues by Randall Gibson will have a leg up on all those swiss army Marks by being stripped down for skinny dipping in the tone pond. I love the swiss army TA and Express but it doesn't work for me trying to recreate the Mark II or III. The swiss armies I like aren't trying to be something they aren't.
I am not going to disagree with you about the S being a great and way overlooked tone machine. The S IIB loop mod was my 1st Mark and my IIC non-plus S is amazing thru a 412 of redbacks. Flux is my 2nd theory of why keeping it simple is key. There is a right hand rule and any conductor with current creates flux as per that rule. The more wires and components the more flux and all the flux interacts making a flux soup and is why layout matters.
Flux is also my guess why for tone the non-EQ Mark II's are more consistantly better than the more sought after EQ variants. Until the Mark III the EQ circuit is spilt up with the 2 boards, each side of the preamp with the wires twisted in with other wires as the signal traverses between the pre and power boards.
Now if big iron doesn't matter and you are regularly playing thru schumacher 180321 and 180322 you could save your back moving smaller and just plug into the board. Lmk when you are ready to sell!