I remember a post someone made way the hell back at the end of HW, found here, that I found to be quite an interesting idea. Basically, by not only keeping, but expanding on the 'cross class' action system, their idea was that while jobs could be specialists, with kits designed around 'doing their job' (eg a Paladin would have defensives), a base class could keep up by using crossclass skills to shore up the gaps in it's kit, while also offering extra versatility by switching out one or two actions on a fight by fight basis.

It also went all-in on the SMN/SCH split and echoed it across every base class. A job that branches off of THM to be a tank? A BLU that isn't locked out of doing the story, in a story-driven MMO? A Healer version of DNC? It's got all that and more. It'd never have happened in any universe though, because it'd be a balancing nightmare. It'd essentially triple the number of 'jobs that can participate in endgame content'