This is all personal opinion, so grain of salt and all that…
You’ve got both a midi interface and a sequencer… If you plan to control the system via midi you might consider using a midi sequencer rather than the Q960 and freeing up a lot of space, or, if you plan on using a midi keyboard you might consider an old school CV keyboard and getting rid of the midi interface (synthesizers.com used to make one, but I don’t see it on their site anymore). Also, note that you won’t need the quantizer bank for CVs generated by the mid interface, though it’s still really useful when combined with an analogue sequencer.
I would try to make room for a Q962 Sequential Switch, not only can you use it to switch between output banks on the Q960 Sequential Controller (giving you up to 24 stage sequences), but can also function as a latch or signal selector!
Consider how much you might actually use the Instrument interface, signal processor, and reverb (okay, reverb IS a must-have, but can easily be handled with an external device to save room) if you can make enough space you are likely going to want either a third Q106 Oscillator, or an LFO to use as a modulation source.
Also, consider whether or not you really need the Oscillator Aid and Oscillator Mixer, the Q106 Oscillators already have outputs for each waveform, so the only new functionality you really get from the Oscillator aid is the soft sync. And the Oscillator Mixer can be replaced with a general purpose 4 channel mixer giving you more flexibility.