You asked for another VCO that might go well together with the Plaits (I would go for the original one, better user interface, which is important, for me at least), I think the Make Noise - STO might be a good choice. I use these two (Plaits & STO) quite often together and I am with both more than just happy, they belong to my favourite oscillators.
-- GarfieldModular
I will not address the whole rack (I have new modules in my rack so burning to go patch those), but since this is between parenthesis here and haven't seen it mentioned elsewhere, I want to direct your attention to the presence of many "mini" versions of modules and what it implies: it's not for everyone, and the more of them you have, the harder it can become for some people to play the system. I say "for some people" because the Erica Pico System seems to be well received but I find it very hard to operate a system comprised of only tiny modules, possible but not confortable.
I guess the point I'm trying to make is please do not dismiss that aspect as being inconsequential and think about whether or not you could be bothered by the concentrated nature of the UI in the proposed rack.
Good luck for the rest of the planning ;-)
Diego
--- Voltage control all the things ---