The other sticking points to a later iteration don't seem like sticking points anymore to me. Build the simplest one and they seem to evaporate with familiarity and practice.

The linestage sounds good. I have not listened to it with the single MOSFET plate load CCS in a ling time. It is easy to modify it to a cascode circuit later. The single *IS* simpler and easier to deal with at first. I would not have suggested it if I were not confident in the result.
regards,
Douglas