Hi Peter,
Forgive me for being the hare (the rabbit) that hops ahead and looks down the road to see what's there, while the tortoise (the hard workers) labor deeply on the mathematics.
I want the physics community to discover gravity field generators. I would do it myself if I had the talent and the energy needed.
I see the flaws in superstrings and quantum loop gravity because strings and loops just sit their and wiggle. But whatever the universe is made of, it has to explode and expand quickly (perhaps even faster than the speed of light) because that's what the big bang did.
I advocate for the idea that gravitons really do exist. But they begin as points (perhaps from the Planck scale) and they expand at the speed of light into spheres that overlap with other expanding gravitons. The idea is that all of these overlapping gravitons produce the effect of a spacetime continuum. I think that the Einstein equations are describing an equilibrium of expanding gravitons.
But this is the part of my idea that I'm quite proud of. Every quantum mechanics problems is solved by calculating the wave function. So does the wave function actually exist? Some people think it does; I do. But I think that the wave function is what happens when an expanding graviton collides with a particle, it becomes a trapped graviton.
Wave functions have operators for momentum p_x, position x, energy E, etc. In quantum mechanics, you can calculate the expectation value of momentum states, position states, etc...
I think that the graviton has quantum states for position, momentum, etc., built into the expanding graviton.
If you ask me what spacetime is ultimately made of, I would argue that it's made of gravitons which are made of quantum states for position/momentum, therefore, spacetime is made of quantum states for position/momentum.
There is an experiment that can be performed if you have an appetite for it.
JW