Using you with an attributive adjective (which is to say an adjective in front of it) is generally interpreted to create a third-person reference to the listener (or reader). The same goes for me. Thus you might hear things like
If I go to the trouble and expense of earning a college degree, future me will appreciate the investment I made in them
where the antecedent of them is “future me.” (Note too that in such usage, the subject of the clause is expressed in terms of me and not I.)
Thus, dumb old you could easily call for wants. I would add though that the noun phrase dumb old you strikes this native speaker of American English as an odd turn of phrase.
And here’s an additional warning. As pointed out by @FumbleFingers in the comment below, the personal pronouns are not a class of words that typically accepts modification, so most uses of such constructions are quirky in tone and anyway fairly nonstandard. So learners of English should probably avoid them. My example, for instance could be rephrased along the lines of
If I go to the trouble and expense of earning a college degree, I will afterwards appreciate the investment I made in myself.
(There are a few counter examples that are safe because of their wide usage—things like silly me! and poor you!)