Back when I was a frosh, investigations actually meant something. Mafia had 1 MtP, 1 frame, 1 hitman, and that was it for confounding investigators. I think it says something that not only did mafia's kills go don, mtp, hitman, don, but town called that this was probably happening and it was STILL optimal for mafia to keep doing it. I would actually be really up for getting rid of don because of this. MtP and hitman used to be strategic (e.g. MtP can cover up a quick kill you do to keep someone quiet), and I think there's really only one correct way now (modulo swapping hitman/MtP order).
I had also forgotten about serial killer amidst the frame/group investigator arms race. As it is, serial killers are super weak, which is sad because they should be an awesome role. I do like frames being done at the time of the kill, because it rewards mafia for thinking through good culprits ahead of time rather than just framing in response to town discussion deciding that someone is sketchy.
Mafia do not at all need to be stronger early game and weaker end game. Mafia found out roles, saved up traps, and got a kill spree they deserved. IMO, mafia actually tend to be weaker late game, because the meta forces them to use up investigation manipulation abilities early, and a lot of town roles are absolute numbers (gay knights and desperadoes) that are strictly stronger to have alive late game.
I agree that stalking is too much dictation. Possibly letting mafia stalk more than once a day would help (then town can't prove that at most one stalker is mafia).I like the suggestion of only letting mafia aligned players know when they're being stalked, but I kind of like the idea of vigilantes being stalkable too... Especially because vigilantes should be able to fake serial killer.