USTA is another I've considered. Looks very good! Also out of stock at my vendors : (
As I continue to try to wrap my head around the possibilities of multiple sequencers + downstream logic & utilities, it occurred to me "I could model a lot of that in Excel." A lot of 1s and 0s, small integers representing quantized pitch CV, AND, OR, XOR, etc., yes that would work fine in Excel. The main problem is !!!BORING!!!... but I'm imagining a few hours with a spreadsheet would go a long way in helping me understand this -- as I'm still trying to wrap my head around "if I take XYZ basic sequences and push them through ABC units downstream, what outputs do I get?" AND if I get a better grip on that, it tells me better what (if any) additional sequencing capabilities would be useful. I'll post more if I have any interesting findings on this.
In the meantime, I'm crossing my fingers Patchworks (Seattle) might find me an in stock unit I like!