I'm not a muscular guy but I'm well toned and although my leading takes work, I have received comments from women I've danced with that the force I exert is "just right."
Women don't like to be pushed around but they don't want someone meek either. When I first started dancing, my frame was terrible and it was like the women were leading me. Now that I've got a better frame, it feels more natural.
In order to have a good frame, I think core muscle strength as well as being well-toned is more important that bulking up.