You look to be on the right track.
Good choice of first case. I'd suggest removing the Mother into it's own case to create more room but you can come to that point organically as your system grows.
Perhaps look into additional utilites such as switches (quad sequential, et al.).
LFOs also seem underrepresented unless you want OXI One handling all of those.
Maybe a filter?
You may also eventually find yourself wanting additional vcas.
You're probably best off working with the above for a while and seeing what limitations you're bumping up against, and adding capabilities based on that.
Best of luck!!
Edit: I just realized you had polimaths vs. normal maths. Unless you're planning on expanding with Make Noise's New Universal Skiff System, you may be better off running a regular ol' maths? I'm not very familiar with the NUSS, so don't quote me on that, though.
“You must have chaos within you to give birth to a dancing star.”
― Friedrich Nietzsche