I think go for it! The first step of the project is probably to build 3 SSOs, which is a reasonable novice project, I think?
I read your tuning questions to mean that you want to be able to do something like the following - set a group of three oscillators to say a triad, say C, E, G, then have another pot that would let you retune all three at once in a way that keeps the relative distance of each from the other - so you could tune it up using one knob to F, A, C.
I’m am personally sceptical that would work without being really fiddly - I’m not sure the SSO circuits could be controlled with relative precision in that way, as I imagine the choice of transistor would interact with the resistance change in a way that would mean different SSOs respond differently to the same amount of variation. Though I don’t know for sure, I haven’t tried it.
That being said I do have a potential idea on what you could try.
You could create a potentiometer (which will be your master tuning pot for your bank of three) that varies voltage from day 0v to 5v (make this range the same as your CV input I think).
Then create a non-inverting summing mixer with an op-amp to mix your pot voltage with your CV voltage.
Then you need a circuit like this: My build progress - #5951 by savt22
That is four LED drivers. Send your mixed CV voltage into one of the four driver inputs, and then connect the output to the three LED sides of the vactrol for your bank of three oscillators, and wire them in parallel.
You’d get a master pot and cv in for your bank of three that would control pitch, but whether it would control it with enough precision I don’t know.