Dennis.....I would think that it would depend on the coach. Some, like mine, only take the pressure off, but still leave the axle down. Some lift all the way off the ground.
You bring up a good question and maybe it would be smart to have a way to support (chain) your tag if you needed to remove the tires. I think even if you had a liftable tag, removing only one rim would probably make the opposite side want to press down and angle the axle in such a manner as to cause issues.
I think in my case, in an emergency, I would run the tag tires up on blocks, release the air and chain the tag up. Mine would also need the air disconnected as mine goes back into service at 5 mph.
I wouldn't have any concern about the weight on the duals, since it would be an emergency issue. It might be a good project to design a chain with hooks or some sort of connector that would fit, if you needed to chain the tag up.