So yeah! Ghosts in Skyrim are crap-level disappointments and while I've seen people tweaking with stats and skins on them... THEY NEED TO BE SCRAPPED AND REPLACED!
Seriously... how is this for a mod suggestion! Totally create a new floating-style ghost creature that only barely resembles a human in form (more like a ghastly twisting mass of ectoplasm like what we had in Oblivion). They would also be surrounded by a thick fog that obscures the monster's form even more and casts and eerie glow on the surroundings... disappearing and going dark from time to time (with only a faint image of glowing eyes visible). They would also make the spoooookiest sounds imaginable of moaning and wailing and groaning and the like!
While I do think it would be nice to go back to the scheme of Oblivion where they could only be destroyed by silver or enchanted weapons...
I think it would ALSO be a great idea to have another class of these creatures that exist only as phantom images to confuse and bewilder the player. These ones would only be subtly different from the hostile ghosts and would not attack the player nor can they be attacked or killed with any weapon... rather they can only be de-materialized via a Magelight or Turn Undead spell. This would cause a player to be on edge... not knowing what ghosts are just tormenting illusions and which ones are hostile spirits.
To be honest I'd almost be fine with just having the non-hostile ghosts to add ambiance and spooky atmosphere to areas too!
I think there are all manner of places in the game that would do well with having a population of these things. ESPECIALLY the swamps in Morthal and various ruined structures in the game! Replacing the big disappointing ghosts in this game with something floaty... and spooky... and totally NOT just a re-skinned cop-out of the awful cop-out Skyrim ghosts! We neeeed this sooo muchhh!!!