I don't know about "change", but I would probably travel back to after the release of 6DOIT and try to encourage the band to take more risks and experiment more with their music. I think quality aside (some people on the forum loves the more latter releases, others feel the opposite way), I still think it's safe to say that DT used to be more adventurous back in the day. I&W was the big classic, Awake did not try to replicate the same formula, and for good or bad it came out different. FII was bothered by studio interferences and it also has a unique charm of its own. Scenes From a Memory was just epic, being a concept album and all. 6DOIT had the very ambitious themes and pulling off a 42 minute song was quite epic.
I feel like they have played it very safe since then. It's not like they need to change, and I would imagine at the age they're at, it's comfortable playing to your sure bets, because you know many of the fans are along for the ride. (no pun intended) Still, there's so much talent in these guys that I would have loved seeing them do more experimental things, or at least take bigger risks. Maybe encourage them to make a Metropolis Part 3 album.