Alternative Sense Perception Checks, ...so I yelled to the cabbie, Omae, smell ya later! Options

[MikeKozar]

I'm working once again on my automated Maptools scripts for SR4, and I wanted to get some opinions on rules. What I'm trying to set up here is an automated Stealth system; Team One is designated as Infiltrating, and Team Two as Patrolling. Any time that the GM feels it is appropriate, he can hit a button and any or all of Team 2 will roll Perception, modified by cyberware, stealth gear, etc, against every member of Team 1, in under 10 seconds, without skipping any modifiers. If a member of Team 1 is invisible their token will be obscured from the opposition; if a member of Team 2 has not beaten the infiltrate rolls or been manually tipped off, he will be unable to fire on the intruder.

Now, the GM will always have an override, but being able to handle 30+ skill checks while taking into consideration a half-dozen modifiers to each is very, very tempting. I want to get this as fair and right as possible before I let my team use it. The issue that worries me is non-visual Perception, specifically hearing and scent.

Now, we have agreed in the past that a non-visual Perception check uses the same pool as a visual one, sans bonuses for Cybereyes and vision mods. However, I'm thinking I need to apply some pretty stiff range penalties; I don't think it's unreasonable to say that most people can see farther then they can hear. I'm thinking of adding an ambient noise slider next to the Darkness slider, and have it impact the range penalties for hearing checks. I'm envisioning something like this:

Penalty...... -1.... -2.... -3.... -4.... -5.... -6
Loud.......... 01m 02m 03m 04m 05m 06m
Noisy......... 03m 06m 09m 12m 15m 18m
Normal....... 05m 10m 15m 20m 25m 30m
Quiet......... 10m 20m 30m 40m 50m 60m
Dead Quiet 15m 30m 45m 60m 75m 90m

I still want characters who get one hit on Infiltrate to be worried despite buying the fancy chameleon suit, and making sneaking risky when you get close to guards seems like a good mechanic to include. I'd love some real-world opinions on my ranges, though.

Also, Chemsniffers. I don't even know where to start on that. Flat 25m range, or will I need to track wind speed and direction?