Excellent :). This significantly mirrors my recent thoughts (though I used slightly different terminology), I outlined my plans for a mini sequence in the open thread a few days ago, asking for people to help look over things.

The core similarity is what I call the pattern theory of identity, which, justified by pretty much exactly your reasoning, concludes as you do that "I" is a moving fuzzy category, and additionally that category is usefully defined by "aspects of current-me which current-me values".

I've developed it a bit further and have a load of fun links to explore, to morality, evolution, and a bit more on decision theory.

Would you be interested in working together on writing up and developing a little series of posts based on this? It seems to me to effectively dissolve several things which are otherwise confusing, even beyond the parts you've already covered, which are already important.