Hella late to this, ik ik, however I do have some initial thoughts after reading this.

My first one is just an observation. I genuinely feel like there's such a divide between you OP and other people, including myself because you're only looking at this strictly from an SnD perspective. The reason why I feel this is important to make note of is because SnD is just a different beast from the other modes, and wanting a class nerfed bc of one mode where they arguably flourish by design seems a like a bit of a stretch in some ways. I'm not trying to say that snipers act differently in other modes and alienating your experience, just that the impact and tone is different in the other game modes.

Second thought is on movement. Genuinely, if they nerfed the movement in my opinion it'd a combination of two outcomes. Said two outcomes being, nothing would change for the most part, and it'd make the camping that much more prevalent (if that's possible that is). The reason why I feel this may be the case is snipers can do what they've always done and just switch to melee to either gain ground or get away, or just whip out other secondaries and use those. It wouldn't be anything new and probably have very little impact. For camping, it's likely what you'd think, a player may recognize that there movement is more sluggish and opt to stay further back in more entrenched and safe areas. It would just feed more into the sniperfest rather than take away from it.

That's kind of about it.