Coach board had a pretty legit festival rule system.
I think one of the most important is to have the same number of bands, or possibly just a limit to avoid just a battle of lists, and then some sort of limit on reunions.
A more advanced rule system will be there for the next edition. This one is like a tryout.
I'm not a fan of the same amount of bands. But it's mentioned in the rules section that there's a minimum amount of bands and a maximum amount. This should create a lot of diversity between te festivals.
There's also a limit on reunions mentioned in the rules section.