Gosh, I love Stiles and his dad. And YES Johnny Cage, aka my favorite headcanon for the series.

And really, Leverage is a master class in letting your characters grow without having them turn completely OOC. They all grow noticeably from being part of the Leverage team, but as you say, Parker in the pilot and Parker in the last episode are both definitely still Parker. It's just brilliant, and it's one of the reasons I love the series so much.