Yes it makes sense. It makes even more sense if you then slam a metal pin into the earth and voilà: You have a real earthy-earth.
The point of having ESD straps connected to the Mains Earth is that everything in the world is directly or indirectly connected to the Mains Earth (because it stands on Earth somewhere), so it is the reference point that makes the absolute most sense. But the actual real relevance of the ESD strap is that you are at the exact same level of charge as everything you handle, so that nothing gets zapped and breaks.
So as long as you define a big metal bar or thick wire as "this is my earth here" and connect everything through the methods intended for ESD to that central piece of metal, you will be achieving the exact same thing again.
As said, it is best, for noise effects and such when measuring things, to actually connect it to actual earth by poking a metal pin into the ground somewhere a couple of feet or at least 1m deep, so that the ground you walk on acts as a referenced ground plane and all the earth connections of your devices again react to the environment as they normally would, but if you can't, then the least you can do is connect everything together and call that a safe reference point.
Of course if you are doing that, you do need to keep an eye on: Am I keeping it safe? You must make sure no current can travel from one end of the generator to the other end using your nifty floating (or actual) earth bar, or you might be creating health hazards.
Usually, with most common ESD safe equipment and straps there's a 1Mohm in all the "dangerous" paths that would protect you from harmful currents, but it's better to make sure they can't even happen, than to rely on one single mode of protection.