Video of slap & fold sourdough brioche
I just spotted a video on the excellent Swedish blog Brödpassion ("Passion for bread") which shows that it is in fact possible to slap and fold brioche dough. Not only that, the end result looks marvellous! I guess one will have to buy his book, "Den Franske Bagaren" ("The French Baker"), to have the formula... Link to video here. 
There's some wonderful photography and stories on the blog as well, all in Swedish but with an option on the right hand side of the page to use Google for translation.