Tegmark level IV is a very useful tool to guide one's intuitions, but in the end, the only meaningful question about Tegmark IV universes is this: Based on my observations, what is the relative probability that I am in this one rather than that one? And this, of course, is just what scientists do anyway, without citing Tegmark each time. Hardcoded universes are easily dealt with by the scientists' favorite tool, Occam's Razor.