Well, no to compulsory, but it would be improved with more cars. As a regular Le Mans goer, I attended my first Daytona 24 hours this year. The really big thing that struck me was that the field was about twice the size of Le Mans and the track distance about a third. Result action all the time and still plenty the next day. So yes an equivalent lineup of about 250 cars would add a lot to Le Mans.
So maybe you do need to make it compulsory to get that many
