There are a large number of people that love to be regressed to a simpler time: their youth. Infantalism is fine, but it's not my thing. The part of this fantasy best left in your head is the brainwashing. People are very programmable, and it is scary how easy it is. (Just look at women's magazines and advertising in general.) The main reason for me is, so much could go wrong.
I think that this is one of those things, like breath control play, best left to a highly qualified medical practitioner. I'd want to see a full set of confirmed qualifications, before even talking to someone about it, let alone considering it.
Anyway, the fantasy is an entirely safe place for it to happen.