Well, aren't you Mr The Glass is Half Empty today!
I'm just trying to save the tootsies(toes) of my fellow gamers! We're such a physical bunch, I don't want to see anyone's athletic career down the tubes!
......and I think you'll find it's the river that's half empty, not the glass.
Easily prevented just by running a couple of straps around the neighbouring legs of each of the tables so that they can't be moved apart.
Sorted! That's a great idea!
You could really expand on that river idea. Anything from Grand Canyon style depressions to a cliff that leads from the floor up to bunkers on the top of the table for a Guns of Naverone type game!