If by Limit Breaks you mean "A powerful move that can be used once in a while", this surely is something that can be worked out.

I personally think the dev could work out some FFXI 2-hour style skills in term of effectiveness, but putting them or a more unpredictable "cooldown", not necessarily time based.

Maybe having a bar that fills differently by each job, like having the Paladin bar go up by being hit while a Dragoon could fill it by dealing critical hits.