They will return the option of unequipping actions sooner or later. Not removing them would bring issues as the cap increase. About job cross-class actions, seems like (don't remember where i read this) the job will be able to use actions from both classes required to unlock it, like PLD requiring GLA30 MRD 15 would be able to cross-class MRD actions only...if this all confirms, at 50 we already will have 15 actions from class, 5 from job and 3 from cross-class, leaving us with 23 actions.

If not mistaken they said jobs will have an action quest every 5 levels, so if we get a cap raise of 5 levels we will learn 1 action from class and 1 action from job, already leaving us with 25 actions (26 if the cross class action happens to not be class-specific)...if we get a 10 lv cap raise, we will already reach the 29 slots. Even if we have no cross-class actions, with this mechanics we would be locked when cap reach 75 (would means another 5 class actions and 4 job actions, totaling 29).

So yeah, i do think soon enough they will return the option of unequipping actions...probably after adjusting the jobs.