Working on a scenario--any feedback appreciated

[RaidCasto]

This is my first attempt, and I'm relatively new to this game, so if this scenario has already been done better, let me know. My scenario woul be called 'We Found A Cure'. The board would be set up normally. Take out all Townsfolk cards and set them face down in a pile. In the center, put the altar marker (or ooze if you prefer viral zombies). I'm not sure if you would need to find the cure first, with the number tokens, or the evidence cards from the survival deck. The cure could be either the bio gel or cross, book, etc. Next would be to cure a set number of zombies. My thought was if you roll two 1s on any of your fight dice, the zombie was trapped. The hero could not leave the square until all other zombies were killed(can't just run off with a zombie in tow). The hero would have to take the zombie to the center. Any movement that ends not in the center, the zombie can roll to escape, and if so immidiately fight the hero. Once in the center, give up a move to cure the zombie and draw a townsfolk ally. Heroes win if they cure 2-4 zombies.

This is a pretty rough draft, so I appreciate any input. The game is really good at balance with the dots system, what I don't know is time length for objectives. Most games we play almost always come down to the last turn with either side having a chance. I think Flying Frog does a great job at balancing the scenarios out. I don't know if searching for a cure, and having to trap the zombies would take too much time. Any thoughts from the pros?