It wouldn't be hard to do if you used an epoxy putty like taxidermists use.You can build up any shape you want,even mold it to your hand shape.you have at least an hours working time and if you want to sand or rasp,let it cure overnight.It will be fairly hard in 3 hours.
Cover with leather and you won't be able to see the epoxy.If you ever wanted to change it back,rasp off the bulk of the epoxy,sand the last little bit down to the surface of the wood and refinish that small area.
Right now,the best of those epoxies for sanding and rasping is All Game.It also smooths very easily when applying.Your taxidermist may fix you up or check out taxidermy suppliers.
Once you have it,you will fins a thousand uses for the stuff.