Actually, yeah, a couple of things come to mind. You might consider a VC Polarizer such as the Doepfer A-133 for changing envelope (and other) polarities in lock with other modulation. Might be very entertaining to have a filter envelope switching back and forth from positive to negative polarity in sequence, f'rinstance. Joranalogue's Dual Window Comparator is a nice fit with sequencing, also, allowing CVs above/below/in window to fire gates that can be used to add further complexity to sequencing. And a bit of Boolean Logic can work with that as well, turning things off and/or on depending on comparator vs clock states. And maybe one more filter, namely the Tiptop Forbidden Planet. The Steiner Synthacon had a wonderfully raucous filter, and this does a good job of nailing its feel in minimal hp.
Not 100% sold on the PanMix, tho...you only get CV over level on that. Have a look at the Toppobrillo Stereomix instead; the size is good, plus you have CV over level, pan, and FX send, and the 'Cue' function can be used as a second FX send, which would work well with a Happy Nerding OUT to mix that second FX return back into your stereo out. Only four ins, but adding a small submixer (if needed) would fix much of that.