Okay, well, I've successfully driven myself mad, and it looks like Mesa replenished stock.
Would something like the 7i96+7i85s+spinx1 cover my bases?
Seems like it has enough pins to cover 4 axes of step/dir + encoders + 0-10V spindle and plenty of I/O still around for limit switches, a few relays and probing.
It's essentially the same cost as a 7i76e by itself, which is ultimately more expandable, but I'd end up on a 7i76e+7i85s anyways and not use all the I/O.
Even though the computer will sit in the same place as the electronics, having this networked will ensure that I'm not beholden to whatever computer I may end up with (I'm using an old computer, who knows how long it'll last). That's getting me to lean away from a 5/6i25 solution unless there's clear advantages that I'm missing.
Thank you all!
Daniel