Haha, not a fool at all!
I've seen quite a few undead sylvaneth armies that were vengeful forest spirits.
Most ambitious one I've seen is a chaos bog one.
http://objectivesecured.blogspot.com/2017/04/bog-sylvaneth-tainted.html?m=1
As for some ideas, you could save yourself some trouble with the wraiths and just make ghostly pale dryads with swirls around the legs or spirits coming out of them. Hollow creatures that act as a puppet for the eldritch beings hiding inside of it and come out to attack.
Hexwraiths could be just head swapped wood elf cavalry with the reverants and mounts given a ghostly upgrade with bones and branches coming out of their bodies. (The giant insects acting as grubs and emerging from a mount's side could be a nice touch)
If you go the wing route then maybe make them centaurs with a second pair of wooden legs behind them and connected with bones and vines to the main body?
Those are my ideas, at any rate.