Hi Rob!

I really like the idea of the modular being able to play samples so maybe a Grandpa or Qubit Nebulae should be on my wishlist?<

While GrandPa is a sampler, it seems to have a grain synth slant. Nebulae looks more open to me. Also, it can run Csound and Pure Data programs. So quite the beast in a class of its own.

I haven't included any specific percussion or drum sounds as I have a Maschine somewhere that I thought I could use for this and to act as a Midi trigger in the early days (hence the Erica Midi - Trigger module). <

If you don't feel like firing up the DAW but need some quick and dirty sampled drums: D-333
Doesn't break the bank and throws in some lofi wavetable-ish sounds for good measure. Just 4HP too.

I suspect that once I start this, I'm going to have difficulty stopping...

That's conventional wisdom around here ;-)

The modules on the bottom row are my wishlist that I'm having difficulty sourcing.

Even disregarding the bottom row it looks pretty complete to me.
A little light on utilities but you will see what works for you .

Enjoy!