Using delta-time guarantees your game plays the same way regardless of framerate. So I don't believe that's a reason to support a fixed framerate.
Also, isn't 60 FPS with the odd hiccup still a better experience than a steady 30 FPS? Also, why are you sure hiccups won't still happen at a lower framerate? I've never been convinced there was any need to run C2 games at any framerate other than V-sync, since it looks best and provides the best gaming experience.