Stellalator- in another universe we cant call up thermodynamics or relativity because we dont know whether either would be valid in another universe.
I agree with you on principle, but not in theory. You cannot have a structurally stable universe without some form of universal
constants (from which we derive our law of causality between two places of the universe, i.e a sense of relativity, whether or not it is fundamentally similar to out relativity) limiting the speed of information communication. Without those, we cannot have causal interactions between matter and energy. A universe without constants (or very 'sloppy' ones) cannot have a stable internal structure allowing for the formation of matter, regardless of how exotic that matter and what its interactions may be. If multiverse theory is true, then it would be the rule of all universes
with substance to have physical constants like
c,
G,
h etc within them, and thus express certain thermodynamic laws (or similar universal rules thereof). There may well be an infinite number of universes without constants or such exotic ones that there well as may be considered to have none, but the homogeneous nothingness that results from that would make them indistinguishable from being no universe at all.
Ah, but how about the idea of constants that change over time? The idea that the alpha fine structure constant has changed over time has been thrown about for some time. Also, their constants might not be the same as our constants. It might depend on the number of dimensions in said universe. If String Theory is on the right track, and the most stable configurations are 4 and 6 dimensional universes, then we could have an entire class of stable universes that are unlike anything we could imagine (for now, anyway.) Also, we could have different arrows of time in different universes (like a universe with an arrow of time opposite to ours), but the arrow of time would still be forward relative to the rest of said universe. Like conveyor belts going in different directions but still forward relative to themselves. In that manner, you wouldn't be able to compare the constants of one universe to another, but only with respect to itself. If we would ever be able to travel between the two (which I contend would require a transformation from matter to energy) then we might actually experience a different causality than what exists in our universe.
Wat, what you said gave me an idea. Instead of using the Big Rip to regenerate the entire universe using all the matter of the universe, when space-time finally gets ripped apart, wouldn't that eventually lead back to conditions before the universe existed? In other words, a baby universe (or many) could be created after the parent universe is destroyed. To do this, you wouldn't bring everything back together, but each "shred" would become its own causal patch and thus it's own universe. Within each causal patch you could fulfill the conditions you specified regarding density and temperature. Because instead of putting space-time back together, the Rip causes it to be so torn apart that each patch becomes its own universe.
Interesting reading-
https://arxiv.org/abs/1111.4595
Poplawski's concept of black hole cosmology and cyclic cosmology dovetail.
https://arxiv.org/abs/0710.3565
LQC's concept of gravity becoming a repellent force during the Big Bang phase
https://arxiv.org/abs/1304.3122
Planck 2013 support for the theory
https://arxiv.org/abs/1206.2382
Ekpyrotic cyclic cosmology
https://arxiv.org/abs/0710.3565
LQC quantum bounce
https://arxiv.org/abs/1603.05834
Progress and Problems in the theory