Would this be the reference frame of the center of gravity of the universe? If so, and if some parts of the universe are unreachable due to inflation, would that be the center of gravity of everything within the light cone of a system? Sorry if I'm being imprecise, I only dabble in this stuff.
This is a little confused, I'm afraid. The centre of gravity of any system doesn't define a reference frame, it defines a location. For the universe, it doesn't even do that, since 'the observable universe' is a function of the observer: anyone anywhere can look around and observe some universe for 50 odd light years in each direction. Assuming homogeneity, the 'centre of gravity of the observable universe' is just a clumsy way of saying 'my current position'.
The universe does sortof define a reference frame, and it's the frame in which the CMB (cosmic microwave background) is isotropic. In other words: if the CMB looks warmer to your left than your right, that means you're travelling left relative to the CMB frame.
But it would be very surprising if the laws of physics depended on that. (Indeed, special relativity assumes the laws of physics are the same in every frame, and so far we have no evidence to contradict that).
Interestingly has this in common with tangherlini relativity... which, iirc, also has nonlocal effects (haven't done the math; am not sure)
No one has combined bohm + tangherlini
These days theorists are trying to create theories out of which both QM and GR could arise in the limit. An unbelievable amount of energy has gone into things like string theory and loop quantum gravity. True believers believe that a theory will be found..but they haven't succeeded yet.
Back to pilot-wave theory. In special relativity, no inertial reference frame is privileged over the others. In pilot-wave theory one must be..but no experiment can reveal which one is. This is aesthetically ugly, but not actually a contradiction.