To me, the lvl 3 limit breaks only look right on whitemage(even though they very rarely use it), Monks, and black mages. Yeah I know some summoners like Rydia in other Series can use it but it's mostly black mages and other types of mages that used it. It'd be nice if in the future other classes get their own kind of limit break spell, like summoners maybe cast earthen fury if they have titan egi, aerial blast if they have garuda, etc. while making said egis grow in size or something :P

But yeah I guess it'd be too much work and would take away time/resources on the more important things.