Go back to Chaos Lords being Ld +1? That's still a problem with +CSM, let alone +1 Ld prows, but iirc there's really only a couple of CGs where that's possible, and two where its a likely combination (Retaliator, Nephilim), and at that point they're costlier than some Battleships, so... is that a "problem"? Or does that make sensor prow Retaliators with CSMs or Chaos Lords mandatory for a competitive build?
Alternatively... Is it worth thinking about nerfing CSMs or limiting their use per full 500 or 750 points?