While I'd love to see the option to, if not modify sfx in the CC, to at least be able to silence some powers. Until that time arrives, there is at least the option to modify the game's sfx for yourself. This does not impact the game files in any way and done even back in Legacy without a side-eye from devs, since it's client-side only. Making changes to your own sfx does not impact anyone else, though it will effect how your hear everyone elses' gameplay. For instance, if you silenced Ninja Run, everyone using Ninja Run near you will also be silenced.
You have the option of silencing sfx in the game or changing the sfx to something else, for example I changed MM Bots to squeak like rubber ducks when they walk around instead of "tromp, tromp, tromp" or glowies sound like a pack of hyenas laughing. Check my sig for how to accomplish this.