I've been watching the debate between fay2 and Cilia and, honestly, it doesn't seem to be going anywhere. fay2 has very particular ideas about time travel that don't leave room for Cilia's interpretation of events, and doesn't seem likely to budge.

While, personally, I see Cilia's interpretation as the correct one, what Cilia, fay2, or I believe is ultimately unimportant. Can the writers incorporate more time travel into the plotline? Of course they can. There's nothing stopping them. There's even wiggle room granted by the time travel they've already implemented - while I feel the Alexander storyline seems to support a single-timeline model (even if fay2 would disagree on that point), the fact that Alexander calculated multiple timelines and chose between them indicates that he COULD have picked a different path - something which hints at multiple timelines being possible.

So, yes, time travel could be a future element - even if fay2 is right and Alexander is "preventing changes to the timeline" (I still don't see any evidence supporting that claim, but whatevs). Alex could change his mind, or in his calculations could have decided that certain changes would be permissible and others not - or the changes could have been PART of Alex's grand plan. The writers still have a lot of avenues to follow that do not retcon events as we know them in any way.

Regardless of the interpretation of time travel you use, introducing it to the story is not letting the genie out of the bottle unless you LET it be. The Warrior of Light will never be given a key item that allows them to travel to any place and time they desire. If they're allowed to travel through time, it will be in ways that have strict limitations. Circumstances will prevent the WoL from going willy-nilly on a "fix everything" spree. What those circumstances are, is up to the writers. In fact, it's a silly argument to begin with - we ALREADY have time travel in the game, and it did not let the genie out of the bottle. If we bring time travel in AGAIN, there's no reason that will suddenly change.

As for the Crystal Tower / Gr'raha thing, I agree that you don't need time travel in order to incorporate an optional sidequest into the Main Scenario. However, I personally believe that it's too soon for G'raha to emerge, unless he's fighting a fire of some kind. At the end of the Crystal Tower raids, he decided to guard the Crystal Tower until the world was ready for its secrets. It'd be hilariously silly if the world becomes "ready" less than a year later! If we're going to see G'raha again, it makes sense to me that it would be decades, maybe even centuries in the future - hence the need for time travel. However, if he's emerging for an unexpected development that could be another story. I could certainly see story paths leading to that. Like, for example, Solus's meddling starts to flood the world with light, the Crystal Tower reacts by attempting to bore a new hole into the Void to reduce the pressure, G'raha recognizes this as Bad and leaves the tower to seek help. That would be one way to get him into the picture sans time travel.