I would think it immoral from the point of view of if there are huge risks of it having a disgusting life.
On the other hand, if we could perfect the thing to the point of knowing he would successfully grow, why not ?
For my part I think neanderthals were pretty much humans, but with overly atheltic genes and capacities. I do think the popular picture of a dumb brute is probably far from the reality of who they were, and I wouldn't be surprised if they were just as intelligent as us.