Suggestion: unlimit the cross class system.

[Cabalabob]

The reason why you can't use all of them is specifically because your Job abilities take up those slots when you have your Job crystal equipped - thus leaving you with only five cross class slots to use. So you either have ten cross class abilities available at level 50 for just the base class, or five cross class abilities and five Job abilities at level 50 with the Job crystal. It's a trade off for using a Job.

The trade off would still exist just much broader. Classes would have access to all the cross class skills at once. Jobs would have access to all the cross class skills from their 2 cross classes.