This is a complex discussion because lots of people have different approaches, and also because technical diving is diving that is higher risk and more catastrophic when failures occur. I consider myself a relatively crazy guy. I was Army Airborne. I've been in combat. I've been shot. I'm not going to drown because of an o-ring though.
Really, what we actually need is a manifold that takes a double hose and can be isolated. This is a case where our limitation is the technology. Cave divers operated that way for years, and lots of them died because of it.
The impossible missions are the only ones which succeed. -JYC