Just throwing out an idea:
Friday: Qualifying
Saturday:
Heat 1: Odd Qualifiers (25 laps) (top 6 advance)
Heat 2: Even Qualifiers (25 laps) (top 6 advance)
LCQ (Last Chance Qualifier): Everyone who did not make it through the heats plus the people who didn't qualify (15 laps) (top 2 advance)
Feature: 14 total drivers / 75 laps
Each heat would take under 10 minutes (if all green, lets say 15 with cautions), LCQ would take about 5-7 minutes, and the Feature would take 25-35 minutes (depending on cautions). So if all runs smoothly we can be done within 1h 15m. Sound good?
As for the pits: They are only made for people with severe damage. Autocross has those ridiculous barriers that sometimes can destroy your car, so I made a small pit area where you will be allowed to reset in a pit stall to fix your car. It's not a way to change tires, because the direction the car resets in LFS I could only add 4 pit stalls, so not everyone could dive in under caution.