Setting aside that you revived a ~3 year old topic to post this, I do like that you're forcing the players to spread out. Normally when I played Mafia/Werewolf (card-game TTT is probably based off of), the game really depended on how fun the group was and how well they knew each other's tells. Forcing the players to split up and/or panic outright is a good way to make those issues less important. I'm not sure your solution is quite right- the slasher will be blatantly obvious, could get gang-mobbed at the start, and will be annoying to elminate - but the idea seems like a good one. Maybe make it so players need to get slasher-protection badges/tokens/etc. instead of building something so they don't need to work together and the various sub-groups have a method of eliminating players indirectly (What? Give you one of my three badges? But I need them for people who definitely are not the terrorists...).
In the card game, I've seen added an 'angel' who could revive dead players. The detective was also the only player who could look at cards, but that was with the help of a mod, and killings were controlled one-per-round. Two terrorists feel like enough for a 7-11 player game indoors, maybe not outdoors though.
It still sounds like an indoor gametype though. You couldn't play that at a war with much more than a small group.
I also see you're in Olympia, are you in PaNNC? They just had a war this weekend I missed because I was busy tiling (story of my life though, I've missed every PaNNC war
).
In summary, the addition of the slasher to our game ended up being a great idea. There was no effective way we were ever going to be able to keep the identity of the slasher hidden the way the identity of the traitors would be, so for each round the slasher was identified prior to the start. While the rest of the players stood in a circle for the traitors-identifying-who-their-traitor-pals-were-routine, the slasher would take that time to hide the Titan ASV-1 parts around the playing area.
As for the gameplay itself, the slasher almost always made players run away (in a kind of herding action) which was good for the traitors because it made innocents easier to pick off in the confusion. Innocents never stayed in one group and would often run off alone in different directions, or at most in pairs. Players were also very happy to play the role of a seemingly invincible machete wielding monster. If memory serves, the slasher was killed at least once out of 6 rounds, in a dramatic episode in which a group of 5 players with the assembled launcher stood ready behind an elevator door while the slasher was on the other side, unaware that the players had found all the pieces. Once the elevator doors opened and the slasher went down, the traitor in the group of 5 mowed down the other 4.
Generally speaking, the introduction of the slasher was effective in keeping players distracted and keeping foot traffic moving around the playing area. For this reason the slasher gave the traitors an advantage, even if they weren't strictly working together. The odds of a slasher finding and killing a player who turned out to be a traitor were low enough that it was a non-issue.
To answer your question, I only recently came into the PaNNC community and have not attended any of their wars (yet?). This has come after several years of tirelessly hosting and organizing Nerf related events for folks who are students, and so right now you could say I am on vacation. If I ever go to one I can PM you about it if you like.