Thank you so much for taking a look, and for your reply.

I've been thinking about the rack size for sure. The thing is that I have an opportunity on a great value second hand 104hp case locally, and having looked at case prices it seems I might not end up paying more if I expanded later into a second case, rather than buying a larger one right now.

There may be a problem with that approach that I haven't clocked though, e.g. If I immediately need more modules than 104hp in order to do anything like what I want. Although if that was the situation it might call the viability of the whole thing into question given cost

You're 100% right that I'm thinking of it as a nexus rather than a standalone synth