I've used the CC-Lite in the set Polar Express, the Hogwart's set, the RMT BEEP, and a pair of K-Line Interurbans, any of those would be a candidate. Any fairly small locomotive that won't experience significant loading in it's RR life. Note that certain models will not work well with the back-EMF cruise, specifically the RMT BANG, RMT RDC, or some of the K-Line truck mounted motor models. Their motors exhibit excessive mechanical "cogging" and the cruise runs very rough at low speed with those.
EL CLASSICO, since he just stated it doesn't fit into the Docksider, that's probably not the best choice.