If staff are already trusted with banning people, why can't they be trusted with vanishing? You can see when a fellow staff members is in /v, so it's pretty easy to find someone who's abusing. They'd eventually be caught. In my opinion, the advantages outweigh the possibility of someone abusing.
Yes they might, even if a staff member is online on the current gamemode, and say you're the only one on, you try /msg them and you can't then you know they're abusing and you can report them, I think it is possible for someone to code a timer onto /v for say, 3minutes? So they can't be abusive using it.
Neutral and they don't need to have a /ss command because most players on Mineverse don't / won't get on TS because they know there hacking. What would be the punishment if they did not get into TS? Just a ban? They would need evidence hence the recording before banning. I think you got this idea from a HCF I use to play with you.
I support If we were to freeze the player they should NOT be able to get hit because this would cause a problem. I've seen this on different servers and like how the idea works and if they disconnect while frozen it would result in a ban. I also support /v for Moderators. It would be easy to catch someone abusing it because if someone were to be hit while a moderator was in /v it would pop up in chat as a combat tag. Great idea's regathering. (I totally didn't mention this to you in TS once :P)