These are familiar suggestions that have been suggested before, but it probably doesn't hurt to bring them up again since it has been a while. The game does have a shorter lifespan compared other ARPGs, more specifically to PoE, but not every idea needs to be highly inspired or copied from poe unless it's not only a good idea but also an engine realistic idea. I like the charm idea, but I don't know if it's a good idea for it to be enforced.
Since we're on the "poe inspired train" topic, I personally would also like to see another type of mapping system other than dimensional labyrinth. To be specific, a map system that reuses content from 105-120 uberlevels as enhanced versions with higher alvls dropped by the monsters in these creative maps in the form of Riftstones similar to Dimensional Labyrinth. So it would be like farming riftstones in Dimensional Labyrinth, but these riftstones that drop from those monsters, can open a higher alvl of duncraig or higher alvl of cows with creative twists like multiple Bull Prince Rodeo's roaming around (Old MXL). This would also allow devs to showcase old map designs from previous versions so everyone can see how far the game as come in comparison to the default versions of the maps etc... All topped off with scaling difficulty multipliers for even more loot/fun much like the hard mode gem from old versions. or something like this. im just saying shit that came to mind tbh
But at the end of all this, I don't think it will increase the game lifespan by much because in the end, it's just another form of farming with a bit of variety, higher difficulty and rewards. Even if you could upgrade your 105-120 charms within their respective enhanced version of maps, it would still have players wanting for more because what do after you complete or obtain all these rewards? quit? reroll? do it again but on ssf? hardcore?