The cosmological constant is not a given. Einstein introduced it, then strongly rejected it, and then it got resurrected by lesser mortals. Some physicists think it may die again, or be like the phoenix forever. We simply are too uncertain about many cosmological issues to have confidence in those who assure us that they are in possession of the “final” cosmological paradigm.

Regarding Lorentz frames, aren’t they limited to inertial frames. I don’t know if I understand your point that there is a question of whether to choose Lorentz or Einstein frames. Surely we can’t neglect accelerated frames.

Personally, I like infinite (in both scale “directions”) hierarchical paradigms, which rule out absolute reference frames. On the other hand, as pointed out by Einstein, some frames are preferred for modeling purposes because of their simplifying potential and agreement with observational evidence.