> My point is that the way the universe works, i.e. spacetime expansion, inflation and acceleration (dark energy) could all be governed by processes inside a black hole's singularity
The singularity doesn't have an "inside". See below.
> something we afaik don't have a good model yet
The models that are being looked at get rid of the singularity altogether. They don't try to model it as being made up of internal parts.
> a stellar black hole creates a mini universe through its own spacetime rip.
Some physicists have considered models in which black holes give birth to "baby universes" (Hawking and Lee Smolin are two that come to mind). But these models don't "rip" spacetime; they remove the singularity, which in the standard classical GR model is just a spacelike surface--a moment of time--that represents a boundary of spacetime, and instead just extend the spacetime further on, into the spacetime of the new universe.
The singularity doesn't have an "inside". See below.
> something we afaik don't have a good model yet
The models that are being looked at get rid of the singularity altogether. They don't try to model it as being made up of internal parts.
> a stellar black hole creates a mini universe through its own spacetime rip.
Some physicists have considered models in which black holes give birth to "baby universes" (Hawking and Lee Smolin are two that come to mind). But these models don't "rip" spacetime; they remove the singularity, which in the standard classical GR model is just a spacelike surface--a moment of time--that represents a boundary of spacetime, and instead just extend the spacetime further on, into the spacetime of the new universe.