In cosmology we can not make experiments. So we must make a model and look if it fits with the evidence, rational and empiric.
Rational evidence is that the universe as a whole, including the "other universes" is eternal and infinite (in the sense of limitlessness, no border, no edge, but finite in the sense that there is no outside place or matter or energy).
The prevailing theory denies this, so we have a good reason to look if some other theory, model can accept it.
In cosmology we must make models, presumptions and look which one fits best. The red shift is the only one thing that points to the expanding universe, so if we find a model which can explain it, it is not an obstacle for eternal and infinite universe.
In my opinion all the facts fit my model, and I don't have to make any more. There is the math. The math is that it fits. The evidence does not lead to the prevailing model either, it has been invented to fit the red shift, the time- space of the whole universe, and some other findings but it is not the best way anymore to understand the cosmology. It is too complicated and not rationally sound.
And here I ask for a better model if somebody has it in his mind. I don't think that my model is the best model. My model is maybe not good, but this is a fact with every model because the cosmology is so big and complex thing that the mankind and best science does not yet, if ever, wholly understand it. Every theory is still only a hypothesis.