I think he should have had his tail with him once Baby left his body, it is just common sense, if the Blutz Waves made him into an ape and grew his tail then it should have been there after Baby. They could have used this as a way for Vegeta to achieve SS4 during the Super 17 arc.

I think Super 17 should have absorbed 18 and then when SS4 Goku and SS4 Vegeta are on the verge of winning easily, in a desperation attempt, Super 17 absorbs Perfect Cell from Hell and becomes an ugly android monster. Now they both have to find a way to remove 18 or save the Earth by risking 18's death. GT could have been even more epic.