I think in the future more league host options will be available. Until then I suggest giving the league host the option to give grid penalties would be a good temporary solution.
If I want my league to have a 2 compound rule, I can assign a 10 place grid penalty for breaking this rule. Not a perfect system, it requires the host to either notice the infraction or someone else to report it (then the host can look at the race results to confirm). There's also the possibility of a host abusing this power - which to me isn't a real concern.
I understand, having drive through penalties and stuff during a race would be difficult to implement (difficult to code). But the grid penalty feature seems quite simple and straight forward.