Incidentally, has anyone ever actually mapped the globalvars to see which does what?
I think Akari has done some research into these. They're actually not called much. For some reason the final Sephiroth battle sets one. So do chocobo battles if you catch one. Mystery Ninja, Ultimate WEAPON, Zombie Dragon, JENOVA, and Bizzaro Sephy too. Possibly the other WEAPONS too and maybe one or two other bosses. I think that's it. That's probably less than 20 bytes all together. Surely there's more.
Anyway, back to the statuses. You woundn't want to preserve all of them after battle. Probably just seven or eight. Poison, petrify, confuse, berserk, silence, blind, frog, and mini would be all that I would keep. On top of displaying these out of battle would be curing them out of battle. The appropriate curative items have no out-of-battle functions and adding some would take some creative re-writing. The functions to restore certain statuses would be easy, but getting the out-of-battle item handler to acknowledge those functions exist might be difficult. The entire process could stand some more modularity though....that's an entirely different topic though.
EDIT:
The Global Access opcode references Memory Block 1/2 of the savemap. Without the Wiki I can't tell you want does what, but 0x02 of that is MysteryNinja's starting level and 0x5E is Dragon Zombie has used Pandora's Box.
This made me go back and re-look at the structure of the Battle Variables. I think I have an understanding of what some of them do. For example, I believe 2190 is Party Gil count. I wish the wiki were working and I could pull up the structure of the scene files and see where these mappings go.