Making Gogo "normal"

Also by default the guest character(s) won't be able to learn the spells from the espers, or even cast spells like normal characters - more complicated work will be needed if you were planning on that. Same with Gogo and Umaro.

There's only enough confirmed free SRAM (at least according to the latest RAM map that I've seen) for one additional spell learner. (There are a couple of segments of SRAM that aren't described, but the person who wrote up the map was pretty good about describing, "This looks to be unused," elsewhere, so I'm operating on the assumption that he'd have done the same for those bits if it were consistent across save files.

So yeah, if you want additional characters to learn spells from espers, you'll have to look at some other solutions -- rearrange some SRAM to give one more character their own spell list, leave someone with Gogo's special spell list function, or -- as I've seen someone else do -- code it so that two characters share a spell list. (i.e. Terra and Gogo, for example, use the same spell list, each having access to spells that the other has learned.)