If I understand what you're looking for correctly, you want to change between levels that are functionally very similar (just different "time periods"). In which case, it shouldn't be terribly difficult, depending on what you have in mind.
Consider making certain objects global, for one thing. That way you aren't losing access to important information when you change layouts. (Actually, this solves about 80% of the problems I can think of, from my understanding of your idea)
You'll probably end up swapping around a lot of variables at runtime, each time you time travel, so that you sync up equivalent objects from each time period. Other than being a tedious bit of scripting, there's no reason that should be especially challenging.
Does this answer your question at all?