I looked at the circuit and thought not only of what you suggested but also of what I wanted out of the project as a whole. Bear with me while I roll off my thoughts. I'm not much of a "mid" tone person. On my peavey amp the "mid" stays just south of flat. What worries me about the amp as a whole is that without completely rebuilding the tube section the bass response is only going to be so good. Even with a better speaker the low wattage of the amp can only produce so much clean bass... right? Please correct me if I'm wrong. I assure you.. you know more about this than me. With just a speaker change the highs already sound pretty sweet without being shrill and harsh.
Now speaking logistically.... If you look at the faceplate I have 4 holes to work with. The contour and process (bass and treble) controls will occupy the 1/4" jack and volume locations and the jack will be remounted probably on the back, the gain and volume will occupy the tone and indicator lamp positions and the lamp will be moved right next to the power switch. This way everything stays evenly spaced and the switch stays on top.
Thats just to let you know where my head is at. And I have yet to test it after disconnecting the opamp circuit. Hopefully I can get to that later this weekend but I'm still waiting on some parts to come in. Namely a 68k resistor. May have to rob one from another circuit.