hmmm a tight pack of people with varying bottom bracket heights, crank lengths and pedal styles rounding tight corners at speed without being able to stop pedaling... Oh yeah and a mix of braked and brakeless riders most of whom probably have little to no experience with group riding.

Sounds like a recipe for injury unless by alleycat style crit you mean a race on a short road course with various non-biking activities to prevent it from ever bunching up.