(I'm going based on this informal explanation you gave, now.)
It seems like a system such as you describe could exhibit chaotic behavior. Since the person is going to have to create an environment for themselves from scratch, initial decisions about what their environment should be like could impact subsequent decisions, etc. (Also, depending on the level of detail that the person has to specify, reversibility of decisions, etc. maybe the task of creating an environment for oneself would change their character substantially, e.g. like tripping on an untested psychedelic drug.)
Of course, the utility function produced could be "good enough".
A recent post at my blog may be interesting to LW. It is a high-level discussion of what precisely defined value extrapolation might look like. I mostly wrote the essay while a visitor at FHI.
The basic idea is that we can define extrapolated values by just taking an emulation of a human, putting it in a hypothetical environment with access to powerful resources, and then adopting whatever values it eventually decides on. You might want some philosophical insight before launching into such a definition, but since we are currently laboring under the threat of catastrophe, it seems that there is virtue in spending our effort on avoiding death and delegating whatever philosophical work we can to someone on a more relaxed schedule.
You wouldn't want to run an AI with the values I lay out, but at least it is pinned down precisely. We can articulate objections relatively concretely, and hopefully begin to understand/address the difficulties.
(Posted at the request of cousin_it.)