I don't know what UF's needs are but the campus doesn't sound like it will be a big one. The old JEA tower site, along with others, all could probably be made to work. Sounds like the type of project or catalytic opportunity a downtown master plan would address or provide guidance for.
The presentation Action News Jax showed a few months ago suggested about 14 acres of land was being requested for at least "Phase 1" of the campus. The FSCJ site and the Fairgrounds are right about that much, although the FSCJ plan leaves a lot out as far as buildable area (obviously it's early to assume exact built space, but this is all we have):

The space that appears to actually have buildings on it (parcels 1, 2, and 3) amounts to about 9.3 acres. I don't think a specific square footage number has been given, although the price estimate then was around $200 million to build. The 4-block area I suggested in March (including the JEA/Universal Marion building) is just under 9 acres.
If the city was angling to get UF into the JEA building I suppose you'd want to offer it and perhaps part of an adjacent block to serve as a quad of sorts (or future expansion space if necessary), but that's assuming the city wants to do that more than it's willing to let the Jags have it at the Fairgrounds.
I was randomly reminded earlier that JTA was angling to somehow turn the Prime Osborn site into an innovation campus for UF or similar, but ironically now that UF is actually serious it doesn't appear that site is in the running at all. Ah, well.
