thank you sir... very much appreciate the feedback.
so... have considered the wiring. Originally I planned an electro socket where I'd drill the outside holes and then use a long bit to break through the inner chamber wall. I planned to pre-wire the output using 2 conductor push back wire plus a seperate ground, and then stiffen it with shrink tube.
my path is illustrated below - note that the third ouline in is actual guitar.has approx 3/4" of inside material to go through, then a ~2" gap to the inner ctrl cavity wall. good call on the pre-twist. good idea. worste case I could get a tweasers through the f hole but I think if I just put enough length on the wire, hold the guitar upside down, thread wire, grab it from the control cav side, then thread in the jack I should be ok.
the bigger concern, is the threading. I don't know if my tap set would have anything for such coarse thread. I would have real concerns about splitting the wood right there w/o the proper sized hole. I'm thinking I can make the hole the size of the jack + half the thread, wax the threads, thread it, unscrew it out, then put ca glue on edge to fill in the thread gap and thread back in. wax should allow it to be removed later.
the football or square plate is def an less risky option. then again I'd want it countersunk and doing that at this point... would likely involve chisels or a jig... so more work... and I'm not sure it would look as nice as the threaded jack. further, if I traverse these uncharted waters - I could see using it a lot more. I don't like having to put a nut on the other side of a jack like that. have to factor in a flat spot on the inside... just seems more complicated than it should be.
just thinking out loud here. thank you for stirring the pot!