Hi Dr Wobble,
Ive no real data on either of the transformers ,sizewise the mains tx isnt far off what you might find in many 50w amps ,maybe a little smaller than what you'd find in a vintage JMP 50. There's a couple of primary taps(220,230,240) ,centre tapped HT , heater and interwinding screen. Output certainly used EL84's a pair of em ,and again its a generously sized component . Going with a more hi-fi type setup sounds like a good plan ,would make a more versatile unit in the end as you pointed out .
When you say LTP with active tone , do you mean feedback to one grid of the LTP with tone switching ?
Id probably tend to stick with the more common type tubes, Ive had great success with sovtek hardened EL84/7198 variant ,but I also have a very nice set of Groove tubes 6V6's as well .