A few minor details, if you haven't purchased any of these yet: Quadra is probably best swapped with the newer version Quadrax. Plaits may be better in micro version aka uPlaits (check out Cal synths or the like), same thing, slightly smaller. The Quadra and Plaits may otherwise be harder to track down or be used vs. new. IF that matters to you, may not. :)
My gut feelings, take it or leave it, is a 2nd sequencer may be a tad much in this setup?
In my humble opinion, can't go wrong with a Quadrax/QuadVCA/Plaits (or uPlaits)/Batumi setup. Covers VCA, mixing, envelops, random sources (random lfos from Quadrax, Batumi), LFOs (Batumi & Quadrax).
And plaits is obv a classic.
Best luck!!!!
*Edit: Make sure Batumii II vs. the first one...best to go with the newer versions...
“You must have chaos within you to give birth to a dancing star.”
― Friedrich Nietzsche