Are you using anything external to sequence/clock this? The Shuttle Control portion will definitely make this a good idea not to be wasted, and you can still use your Steppy and Mimetic for modulations/other fun stuff (or vice versa - controlling with the sequencers and modulating with MIDI).
Also, you probably want some more freeform modulation: LFOs, maybe a sample and hold (this doesn't have to be big and fancy), definitely envelopes or a function generator (if you have to pick one, this is a good one because it can be both LFO or envelope). As I said, the sequencers can handle some of this and that's a lot of fun, but a variety of modulations will get you results that will make you feel more like you're getting your money's worth here. Inevitably, you may have to put the Shuttle System back in its standalone case and fill that section with boring stuff to facilitate the other voices, though it will still be great accompaniment.
A Veils clone and an Os are probably good starting points for utilities. Usually people forget this and have more modulation. Not a horrible plan overall and if your goal is more percussive/pinged in nature, you'll probably be doing great for a while. Look up Richard Devine's live case to learn more of what I mean - I just saw him live and while his case would probably get some raised eyebrows on the forum here, he's been doing electronic music for decades and his setup absolutely works great for writing and performance. However, unless you know already why each piece is there (in which case you can just ignore me), it seems like a lot to take on in this amount of rack space without modulation, and you'll end up with relatively static sequences that won't feel worth the money spent.
Think about how much space and functionality is given to the Shuttle System, which is essentially a monosynth (I guess it is technically two voices). All that extra stuff is what makes it an instrument and more than just a Furtherrrr Generator and filter. Try and imagine what it would be like if this rack gave a similar amount of options and playing space to the Zaps and RO'VED (and the QPAS, which is almost more of a voice/sound source/effect than a filter/VCA, and can definitely contribute like a synth voice to a patch even while filtering). How much bigger would it be, or how much more of it would be basic modular plumbing rather than sequencing/clock stuff, voices, amd effects?