FFVI Worlds Collide

I believe giving Espers to Gogo was a problem at some point (Read it somewhere long time ago. Don't know if someone figured out how.) but if we could give Umaro Espers

This was discussed on discord as well. As I understand it, Umaro has no space for spells and they would overwrite other memory. However, I have not looked into allowing him to equip Espers without learning anything from them so he can still get the bonus. I will try to learn more about this. Thank you.

I've actually been looking at this, and it seems Square used two approaches to keep the RAM from being corrupted with spell data.  The first is in C3 preventing Gogo from equipping Espers (Specifically Gogo, though it can easily be set to Gogo+ character indices), and the second is at Magic Point accumulation in C2... it skips over the code that writes to the character's spell RAM if character ID is Gogo or higher.  Perhaps SQUARE felt it would be too confusing to players if Umaro could equip Espers but not learn from them?
I tested it in a version of my ROM in which Umaro's slot has the magic command, and he never gains any progress towards learning new spells (so the RAM that would represent his spell list--which is mostly known rages and menu configuration--remains unchanged).  It SEEMS to be safe... in the past when I encountered RAM corruption it would cause crazy things like changing the window to blue chocobos and then softlocking the game, so it's at least promising.

There is the bigger issue, though, that being that in order for Espers to not be grayed out, the character must have the MAGIC command on their menu.  This too is controlled in C3 (the exact address escapes me at the moment), but there's the trouble that Umaro will pick commands from his list in his entirely berserk state.  I saw this during my first run of the Beyond Chaos randomizer: when Cyan was placed in Umaro's slot with only Swordtech, he used Dispatch every turn.  My best guess for a workaround would be to change the required command for Espers to "FIGHT" and then give Umaro Fight in his character commands, as his tackle/toss/blizzard works as vanilla when he queues that command.