What would you like to see (differently) in the next Final Fantasy MMO?

[Shurrikhan]

Sure, but even if it can be done by anyone that still means someone has to do these tasks, no?

Yes, but the decision of who will do something can include more factors as to who is in the best position to do that thing than just who picked which "role". Essentially, the more deeply designs preemptively specialize those tasks by means outside of combat (such as by role, class, spec, talents, or gear choice), the less players have to engage in those decisions.

Now, there's a point where there's too much going on at once to feel like you're doing any part of it--let alone the parts most attractive to you, which specialization helps you focus on according to your own choices--as well as you'd like, and preemptive specialization can help to keep that in check. But, going too far in the opposite direction means that there's only one choice, and therefore effectively none. Good design has situational best answers, if often near enough that convention (person with X tends to do the X things), player preference (what you want to do), a specific capacity (what you're specifically good at) can play a part in those decisions, but they should always be multiple.

Unless this was all hypothetical in the sense that just because we haven't seen it done well doesn't mean it's not possible, in which case I'd agree and I'd still love to see it.

Sadly, this is largely hypothetical, at least from my limited experience (since midway through college, several years ago, I've had little time to sample many MMOs in full). I've yet to see any MMO, to either side of the spectrum, really nail what I'm talking about. The closest I've seen, oddly enough, would be something like oddball runs back in WotLK (no tank, no healers... well, I guess we just completely rethink all our assumptions about how combat is supposed to work and own that new world) and undergeared and undermanned runs Blade and Soul (where a single missed task meant we'd all die and there were very real and necessary decisions to be made about those tasks).