Jailors are overpowered, but I don't think preventing them from jailing night 1 would do much. The main problems with them is that they are unique roles that can confirm themselves by claiming, that this allows them to lead the town and enforce the jailor meta (though this could be a thing even without jailors) and that they are objectively better vigilantes and escorts. Their first jail isn't really relevant. I think they can be nerfed by tweaking their executions and maybe their jail capacity (limited amount of jails? Being unable to jail the same person twice?). I can't really think of a way to make them less confirmable without a hardcounter.
Changing ambusher's kill message is pointless if there is a medium, and in many case there will be survivors knowing that there is an ambusher anyway. And without the gf/maf combo, mafia can be instantly defeated if the gf happens to be jailed/roleblocked. I think it's better if
tactical mafia kills are implemented instead.
I feel like 2 witches would be too unfair to town. It's not fun when you are not allowed to play your role, and having one witch in every game is already pretty annoying when you are a vigilante. Replacing the exe with a "neutral lynching" slot (exe/jester) could work, though those roles are still kinda unfair due to their kingmaking potential. I don't think town should be forced to think twice before lynching someone suspicious, if that was what you wanted to suggest when talking about the NE slot. I think town should only be wary of misslynches. As much as I like jesters, punishing town for scumreading someone and rewarding evils for playing lazily by claiming jester are things that don't sound very competitive.