Of course he can do whatever he wants and it should be easy to “reinsert” the “original” cut for Fett to line up with the current stuff. (The special edition Sarlac pitt with its … Alien-style extra mouth … seemed to make it more of a "chew the prey a bit before digesting) So the pre-Special edition sarlacc does at least leave the possibility of it’s victims not instantly dying since it is a slow digestion without any “chewing”. So with Fett’s armor and gadgets, he would have a chance to get out.
So at the end of the day, Adywan can do whatever he wants since he doesn’t have to follow any canon or what’s going on lately. However, I would ask if he could at least provide the scene with his color correction so it matches with the rest of the film so people could choose to replace whatever he does to “line it up” with what’s going on with Boba and the shows.
For me, I cannot color correct and am color blind … so having that “alternate” version would be helpful.