Your argument is the reason that I'm still holding out hope that Snoke is Plaugies, but is powerless because he was forced to transfer is essence into a non-force sensitive at the moment of his near assassination of Palpatine. (It wouldn't have worked to try and transfer into Palpatine; force sensitives are rare in the galaxy, and it's conceivable that the galaxy's two only Sith wouldn't make a habit of living in close proximity to Jedi or other force sensitives; and it is plausible that even if one were around, Palpatine would have sensed him in the new body and dispatched him more or less immediately if Plaugies did succeed to find a force sensitive).

Essence transfer into a non-force sensitive character would add greatly to the lifespan on the character, allow him a way to walk around freely without and maybe even join the empire's higher ranks without detection by Palpatine, then mingle amidst New Republic figures (most notably, Master Luke) undetected. Knowledge of the dark side without the power to use the force essentially strips him of the Sith title, so that wouldn't step on Lucas' toes by negating the prophecy. This would also give Kylo a good reason for having regarded Snoke as "wise". Snoke is described as "powerful with the dark side of the force", but in what sense? In this case, maybe knowledge is his only power. As to his ultimate goal, Plaugies was always pretty keen about experimenting with midi-chlorians. It'd be pretty useful to have a walking tissue sample from the Skywalker bloodline around if you're trying to make yourself a new body to transfer into by some means other than the dark side, or devise some way to juice your body with midi-chlorians by other means. Meanwhile, Snoke keeps him on a leash by offering tidbits about the dark side here and there. Nothing powerful enough to make him a real threat, just enough to keep the boy from getting bored and rethinking his life choices. That could also explain why Kylo's force abilities seem so underwhelming in view of where you might expect a Skywalker in his 30s to be in terms of power.