This looks fun, Plaits & BIA give you a lot of sonic possibilities. The FH-2 looks like a good way to get MIDI to the sound sources, what are you going to use to get clock and do sequencing etc?
It's a common refrain to mention tight rack space as a drawback. I can also see a benefit in that the constraints of less hp means that more research and planning will go into a careful choice of modules—and (by necessity) will tend to yield a quite focused rack.
If there are a few modules that you end of replacing or adding as you go, and you run out of rack space, the extra modules can go on the shelf for a future, bigger rack, or an additional rack. There are more and more affordable rack options becoming available. Not a huge problem to tackle.
Also there are space-saving micro plaits to consider, I have the Tall Dog one that comes in at 8hp.
Have fun & keep us posted