Consistency is about logics, while Tegmark's madness is about mathematical structures. Whenever you can model your own actions (decision-making algorithm) using huge complicated mathematical structures, you can also do so with relatively simple mathematical structures constructed from the syntax of your algorithm (Lowenheim-Skolem type constructions). There is no fact of the matter about whether a given consistent countable first order theory, say, talks about an uncountable model or a countable one.