It seems as though one may navigate seamlessly between "regular" playing and slide. http://accessories.musiciansfriend.com/product/JetSlide-Nonsleeve-Guitar-Slide?sku=365400 I'll be making an online order tomorrow and I'm thinking about adding this in. I think it's a great idea in theory, but do they really work?
Check with Bonnie Raitt, Eric Clapton, Derek Trucks, and Sonny Landreth to name a few. I've never seen any good slide player using one of these. If they were so convenient, you might expect someone of note to be using one. It looks damn awkward to me, and I'm a slide guitar player. I read through the reviews on the MF page, most people had at least one objection to it. No, I have not tried one, this is just my .02 cents, gut reaction, IMHO, YMMV response.
The players you mentioned -as well as a million more- are old schoolers set in their ways. This thing is kinda new, so it may take time to catch on, provided it's good. I think the key is the ring size. The wrong fit will ruin it I imagine. The thing will have to be snug, but not so tight that it becomes a problem when the hand fills with blood during playing.