I think funding can be a problem to consider, until the moment of success in human trials. But I don't think funding is a problem that really can stop or slow down the process alot, just in the beginning.
Body rejecting is hard to imagine as a big problem, like other users said, it is from your own body.
Failure yes, that can occurs, but since they typically test it in animal that have skins similar to humans (pre-clinical), like pigs, then if a problem occurs I don't think that can delay for 1 decade or drop the process. Just minor changes requirements.
"FDA approvals", I think it should be a minor problem. Since it will have alot of money and interest involved. I don't think FDA can stay as a barrier to a big interest from people.
By the way, I said alot "think". Of course, it comes just from a opinions of alot of people (including very informated people), optimism and by checking the interviews of the frontend of hair clone. There is more sense to conclude that is not TOO FAR.
And funding is a problem that are occurring. Tsuji is the clear example for it. But I think Stemson and TissUes have enough financial partners to do the research without problem. Of course, it is very good.