I'd like to see a Group 3 list of Merits. Combining what I saw elsewhere about modified 2hrs or abilities with a longer recast than that, perhaps this third group could contain such things.

I do think, however, that such powerful abilities would each need to have some "take", if you will, to give players something more to consider when selecting them.

For example: (Using a suggested) 72-hour recast ability would mean no skill ups or EXP gain while its recast is not at 0.
Alternatively, said counter being above 0 might add 10% to all other recasts.
Like the 2hr, I think such an ability would also make sense to share its recast with all other jobs.