I watched Leverage until last season. I thought the first season was the best, partly because I loved Maggie, Nate's ex-wife, and she was in during those seasons. I felt bad that in the first season Elliot was identified as a retrieval specialist and then by season 2, he suddenly got downgraded to "Hitter" with superpowers. To me Elliot is the super smart guy with great skills who also knew how to break into places and retrieve all sorts of things.

I couldn't agree more that Nate is the most boring character and Sophie is up there with him. I never bought the romance.

Although I don't read a lot of Leverage, there is a lovely lj community that does recommendations in all sorts of fandoms here is the link to the Leverage recs http://crack-van.livejournal.com/tag/leverage Most of them are cross-overs and I've read a few of the White Collar/Leverage ones and they were good. I can't say if the stories here will answer your needs or not, but it is a place to start.