A request for opinions and critiques of a new system

In the near future I shall be running a LARP at a local convention. The event is four hours long, It shall be set in modern times and shall center around the events of a subway car full of average citizens who have never met. In the past I have used either Minds Eye Theater rules for more combat oriented games or pre-generated character bios for free form games. Because of the unusual state of having no character interpersonal relations at the start of the game I have decided experiment with the game system in an attempt to innovate (not to mention reluctance to write 50 pages of bios for a 4 hour game). The players shall be given the following sheet along with a character formatted in manner outlined below.

Welcome to Manhattan Underground<
Archetype: This is the single word or phrase that your character is to be based on. This is not the end all and be all of who your character is, but it is a defining attribute. (Examples: Doctor, Mugger, Old man)

Characteristics:
Intelligence: Your body of general knowledge and reasoning skills.

Body: Your overall health, strength and fitness.

Alertness: Your ability to notice things, either in the environment, or in the actions of others.

Sanity