It can stay in the bar just like that other table stayed indoors. As long as the instrument has a clean shot at the table it doesn't have to be on it or next to it.
You are way out of your depth when you start talking about what lasers or telemetry can't do.
Since less than one in a hundred Starrett levels are used to level pool tables I somehow suspect that isn't what they were designed for. I owned a few thousand dollars worth of Starrett measuring tools from the sixties and seventies before they were stolen. I own a zero to a half inch Starrett mike now that reads in ten-thousandths, cost over a hundred dollars. The Starrett wasn't as accurate as a fifteen dollar chinese piece of crap with an analog dial on it until I sent it back to Starrett. I told them about the chinese mike. To add insult to injury, the chinee mike came in a wooden case, the Starrett in a cardboard box. It cost me another ten dollars for the case! I once owned a Starrett dial indicator that was a thing of beauty. Dropped a hundred on one a few years back, it wasn't any better than the fifteen dollar harbor freight one. Felt like it had sand in the gears!
Starrett was a hell of a fine company fifty years ago. Today, not so much. Harbor Freight was handling a Starrett level. Need I say more?
Hu
Tell me something Hu, how unlevel does a table have to be, before a ball will start to roll off? What's the give or take, you know, the +/-?