Yes tbone, that's one of the ways I will try. I just don't have bungee yet (silly diver without bungee!), it's on it's way. But I'm afraid that way it may cause a bit of a problem when adding a second tank.
I've been suggested to put it on the butt d-ring, even though it starts to get a bit crowded there. I'll try both and see which one I prefer.
I would keep steel bands on my tanks, even rental (which is actually what I do). A small screwdriver doesn't take too much space, I do it with my swiss knife that's always in my bag anyway, and it takes 5 seconds to swap the band from one tank to another. I assume your "setup" is simply a triglide on the band and you run the leash through it? Or is there anything fancy that could be interesting to see?
If you're worried about having tools with you, does that mean you don't have anything to change o-rings on your regs/tanks with you when you go diving?