There are two fundamental flaws with the email.
First, the majority of flights are under-blocked. Which means unless the flight departs early, it will be late arriving. So the simplistic approach of a hard rule prohibiting early departures will just exacerbate the issue of OTP.
Secondly, the root cause of the problem is not lack of stands. With 179 stands on the field there's plenty of parking available. The problem is systemic understaffing of ground support personnel. Hire enough manpower, and 15 flights arriving half an hour ahead of schedule will not throw a wrench in the system.