FFVI - Certain Characters learn magic help

You could even replace the Magic command with the somewhat-broken Summon command, so they can still use their Esper. Warning: the Summon command doesn't use MP, so it's easy for a player to abuse it. Keep this in mind when you balance the abilities of Espers if you go this route.

There's a patch that makes the summon command usable, and I tweaked that patch if you were to use it with the improvement patch by darkmage.

Alternately, if you want various PCs to all learn Magic, but only certain spells, the best way to do that is to make it so that only certain pieces of equipment teach the spells you want. And then make those pieces of equipment only available to certain PCs. (This method means that you need to edit the spell lists of various Espers and also Terra's and Celes's starting magic lists so that only the equipment piece teaches a 'unique' spell.)

Nice idea :p