Posting again while it's on mind, I would just straight up lose the extra channel expansion for the Performance Mixer. The mixer already has 12 mono ins and 2 stereo, which if I'm seeing straight more than covers your voice count. That would put you that much closer to something like the AI008 Eurorack Matrix Mixer or whatever else you'd like to add.

Also if you're going to have a mult in your case it might be wise to make sure it's a buffered mult for pitch cv. It's really easy to buy cables that already mult for you, personally I don't see much point in having a passive mult in a tiny case (unless you want to send one modulation to 3 other sources, that's harder with cables).