TGB, you're right that Jake became kind of aimless in later years. In a fanfic I am probably a long way away from posting, I decided to have the character get called out on that fact. His (in my opinion) lack of ambition is something that I wish we had seen be more of a source of frustration to Sisko, but at least we saw a certain other character who most certainly was
ambitious confront him with it later on (though not in the best or most mature way).
As far as the contribution to Changeling mythology, it's also quite bittersweet to see how the little girl genuinely appreciates Odo for who he is--and it seems not just
because he turned into a top at the end--and contrast that against the Founders' extreme xenophobia that no solid could ever be trusted to deal with a Changeling as an equal again.