On paper I would love the ability to level one class and get two jobs, one could argue summoner/scholar in it's heyday was superior to other jobs due to that nature.

That being said in practice it causes too much issues (having them linked the way in the OP doesn't make sense either, because while they've changed a bunch of things on summoner and scholar the base kit is still "similar" and shares some things... the other ones wouldn't).

The reason why the devs also didn't want to ever do this again is because it caused way too many balancing issues... and we already have enough lore problems without making it worse by linking things that aren't connected (even if you got the lore right were back to square one of them having balancing issues).