Why wrong: if you are seeking lowest complexity description of your input, your theory needs to also locate yourself within what ever stuff it generates somehow (hence appropriate discount for something really huge like MWI). Why stupid: because if you don't require that, then the iterator through all possible physical theories is the lowest complexity 'explanation' and we're back to square 1.
Are you saying that MWI proponents need to explain why observers like themselves are more likely across the entire wavefunction than other MWI-possible observers? That's an interesting perspective, and a question I'd like to see addressed by smart people.
That too.
My main point though is that you can't dispose of the code for generating the subjective view complete with some code for collapsing the observer (and subsequently collapsing the stuff entangled with observer). The 'objective' viewpoint doesn't suffice. It does not suffice to output something out of which intelligent observer will figure out the rest. With Solomonoff induction you are to predict your input. Not some 'objective' something. And if you drop that requirement, the whole thing falls apart. It is unclear whenever the shortest subjective experience generating code on top of MWI will be simpler than what you have in CI, or even distinct.
Series: How to Purchase AI Risk Reduction
Another method for purchasing AI risk reduction is to raise the safety-consciousness of researchers doing work related to AGI.
The Singularity Institute is conducting a study of scientists who decided to either (1) stop researching some topic after realizing it might be dangerous, or who (2) forked their career into advocacy, activism, ethics, etc. because they became concerned about the potential negative consequences of their work. From this historical inquiry we hope to learn some things about what causes scientists to become so concerned about the consequences of their work that they take action. Some of the examples we've found so far: Michael Michaud (resigned from SETI in part due to worries about the safety of trying to contact ET), Joseph Rotblat (resigned from the Manhattan Project before the end of the war due to concerns about the destructive impact of nuclear weapons), and Paul Berg (became part of a self-imposed moratorium on recombinant DNA back when it was still unknown how dangerous this new technology could be).
What else can be done?
Naturally, these efforts should be directed toward researchers who are both highly competent and whose work is very relevant to development toward AGI: researchers like Josh Tenenbaum, Shane Legg, and Henry Markram.