Other MMOs I've played have had a storage gimmicks where if you are on a capped character, you build up exp in said storage (to a certain amount) that can be used to fuel EXP into another character or class. This probably wouldn't be terribly difficult to implement if it was a server based function players interact with and our characters can be the multi-job so we can switch to new job and reinteract.

The question is would SE implement something like this clearly knowing it would interfere with the profits from the jump packages. Kinda doubtful there.

As for what the game is designed for, you have many options to choose from and goals to work towards that don't include raiding but if you barely have time to keep up with MSQ, I'm not exactly sure why you're worried about not properly utilizing EXP benefits at level cap. You sound like you dont have time to play anyway.