Whilst I'd like new roles as they add a different dynamic to the game, I don't think it's really feasible.

But they can take an existing role and add abilities to do that allow it to fulfill other roles that may be useful in certain content or mechanics, though people seem to prefer a more streamlined approach, but there is a thread suggesting adding back things like crowd control. This in a way is a separate role, but any job could fulfill it. You may have mechanics where crowd control would be effective, but I'd argue this is something that if implemented should only be a part of newer game mechanics rather than retroactively added to existing content.

Failing that, more Eureka-type endgame content might be where that kind of thing would be more welcome, maybe even job specific abilities that are only accessible with the Magia board in Eureka-like content. So RDM as an example might get more of their CC abilities from say, XI. BRD & DNC might then have a lot more useful things in the way of support abilities and so on. But I expect for the sake of balance, they'd do anything job specific, but I think if introduced it's where I expect it'd be welcome as we already have Logos actions.