If they do something like this, I wouldn't want them to put any more work into it than offering a mog station credit of some sort that would allow for a free story and level skip with a new expansion purchase. The credit could be used for something else if the player didn't want to skip anything. It also serves to point them to the mog station optional items so they know what's available there.

I've taken seven alts through ARR's msq (three of them through HW as well and one through SB) without any story skips. The first few times, I watched most of the cutscenes because I like the story. When I was trying to rush a couple of them through so that I could do the FFXV event, the easiest way to burn through msq was to purchase a level skip, unsync all the dungeons and trials, and skip all cutscenes. ARR can be done in a single day at that point (minus the patch content).

I do think that ARR in general (and the post-ARR patches in particular) could use some pruning so that they don't meander so much. Nothing massive, just some housekeeping touches. HW and SB are more or less fine as they are.