Lore wise, ghosts (and demons) have nifty powers of ownership & possession – and this is often a nifty game mechanic. In fiction-fantasy they take over the most ridiculous things from cars, to people or even entire houses – going out and about wherever they like. Its just fun.
This tradition is continued in 5e. The ghost continues to have this mechanic, at least on humanoids (no mention if dragons, giants or other sentient beings have ghosts, but i digress). Demons also have mention of this in their description (monster manual) and they can take over objects – though the actual mechanic for how a DM should run this, or how & / or who they can then take over, is not mechanically developed (please correct me if i am wrong on this – such rules or rulings would TOTALLY ROCK).
This brings us to the question (above): when clone spell is cast / matures / 120 days, they get a perfect (albeit scar-free and possibly much younger) humanoid-version of the cubic-inch of flesh humanoid target-component. Groovy! When this OriginalOwner of that said cubic-inch-flesh-person ‘DIES’ (zero h.p.? chooses to leave? not turned to undead?), their soul (&/or spirit?) leaves their body and just goes over (astral? as a ghost? etherial? teleports? warp factor ten? speed force?) to their BodyPrime / Clone location. Wakes up (full hit points? all spells? remembers their death? PTSD?) and is ready to take on the world. Easy!
Assuming that this 120 day+ Clone body is Primed & Ready For Action, why can’t a passing ghost (or demon actually) just, you know, take over for a bit? Or why not forever? Why leave if / when knocked out (‘zero hit points’) – as there is no ‘imprint’ from the original host-flesh-bit’s spirit-soul-essence? Why can’t a wizard (or bard or Nagpa or powerful dragon caster… or whatever) just go into full-on business pumping out bodies of Brad Pitt when he was so sexy… or any actress named ‘Jennifer’ for that matter… or virtually anyone it can get a cube of flesh from whilst adding Gentle Repose style magic?
SO MANY CAMPAIGN IDEAS!!!
But wait a moment! How much of this is actually RAW? Luckily we have the Good Lads (and Ladies) from StackExchange to tell me what’s what. Here the good folks tell me that i have had way too many magical mushrooms.
In Short How do ghosts (&/or any alien spirit such as a demon) interface with a mature 120 day+ clone body? Can they take it over temporarily? To what extent could / would this function as a Home Body for that creature?
Honestly, this would be fun. One can imagine an entire D&D version of Altered Carbon… but we must respect the 5e RAW. Just what is that exactly?
Also: i get that this question is poorly written (‘entertaining but not concise’). I will gladly modify this in order to meet the stoic (dour? terse?) restraints required by the StackExchange Mod-Editorial community! = )