Quick update & info: this project was going to involve an experiment using 9s Campy Mirage and a Shimano 9s cassette (as I had the old Mavic wheelset w/Shimano hub already). My searches here and elsewhere revealed varying opinions on how well this would, or would not, work. I got it to shift decently on the stand, by setting the limits and lining up the middle of the cassette, and any cumulative error in cassette spacing vs cable pull (by the time you shifted 3 gears away from the middle) did seem to be "acceptable", if not perfect, at least on the stand.
Then it dawned on me that my "old heavy" Bianchi Sprint 76 has a decent 9s Campy Khamsin wheelset on it. I had previously put ergos on (for a "neo retro" project), but decided last year it'd be fun to reinstate the DT shifters, using old SunTour friction shifters from the 80s, which pull enough cable to cover the 9s cassette. Since the friction shifters don't care about cassette spacing, and the 9s Campy Mirage shifters do care, why not swap wheelsets?
An easy fix, as with the 9s Campy Khamsins with a Campy cassette on the Fondriest, the shifting is perfect (at least on the stand); and the Mavics with a Shimano cassette on the Sprint 76 w/friction DT shifters that are ignorant of cassette spacing, that should be absolutely fine too.
Now I only need to finish painting the seatpost, get a binder bolt from the LBS, and I can do some test rides this weekend.
One more reason - as if we all needed another - to have multiple flavors of bikes hanging in the shed.