I've ported all extdata to the base game. So technically its the same preservation that the game would have if you didn't change the clock afterward, I have figured out which values in the save data are responsible for the lockout from changing the time of the system, and changing them to 0 and nullifying the time offset on your console would restore access. I've also made the comps act like regular boss stages due to not immediately knowing a better solution. While I'd love to make an update to PSSE to add the feature to make the offset of the save file zeroed out I can't program, so I unfortunately can't. Though I will suggest nullifying the offset of your console and checking in at least once before shutdown to avoid the hassle if you end up needing to change the clock, as once its nullified on the save file, its pretty much good to go for life. As a bonus, I've also ported DRI over from mobile, though that feature isn't as useful for people who are already using PSSE to get around farming.
The rotation that is ongoing right now for specials will last until 2037 if you don't get locked out though, so like 14 years for me to think of a better solution. Ideally I want to learn to make a code edit to the game to get around the lockouts and the fact that using the mod requires downgrading the save file back to 1.5.0. First priority though is making sure the extdata is still accessible to people who wanted to try the game on 3DS after the shutdown happens.