You have made EXCELLENT choices. My feedback:
Voices: Qu-Bit Surface--I use this all the time, and like it much more than Rings, but I love Rings also. The 2HP Pluck is also incredible, but only does one model (Rings has 3 and Surface has 5)
Sequencing: Qu-Bit Bloom--my favorite sequencer--2 tracks of up to 32 steps each, with variations.
MI Stages--fantastic, love it!
Utilities: Maths*, Disting MK4--yes, and yes. I also highly recommend Ornament & Crime, which does different functions than Disting, especially if you use the Hemispheres Suite alternative firmware.
Mults--I would recommend one or two buffered mults in 2 HP--put in the middle of the two 3U rows. I configure my cases with two 1U buffered mult tiles at the extreme R and L of the 1U row, and than one 2HP buff mult in the middle of the bottom 3U row, so I'm never patching far away from one. Don't waste HP with passive mults.
Effects: Beads--YES, or a 8HP version of Clouds--I love them both.
Mixing: Quadratt--I use Quadratt for attenuation of audio or CV, and use Mixup to mix up to 4 tracks (2 mono, 2 stereo) to the 1/4" stereo outs that are built into the side or back of my cases. Thank you for reminding me that it can serve as a mixer!
In-Out: Intellijel Line In Out--YES, or use Mixup or something like it.
Well done. Get just one Veils, and then see what you need as you patch. Enjoy!