Certain designs are better suited to different lines I think, the ones that make the best Revoltechs are usualy the more exagerated looking characters with flowing capes, unsual shapes, battle damage and crazy poses. These work best for the semi pre-posed Revoltechs in my mind, while more traditional mecha or characters like TF's are probably better suited in other lines with more standardized articulation set up.
Ever since
Dangaioh was released I've longed to see Revoltech Escaflowne mecha, the unusual shapes and capes would work well in a Revoltech format. More Trigun figures would be good too, but I don't excpect them, as the two released next month are probably just because of the new movie.