Hey Mattias!
Thanks for checking in about this, that sounds like an awesome idea.
I’m the Head of Legal at Patreon and happy to help with this, although as a quick disclaimer this isn’t legal advice.
The TLDR is that as long as your “best failure” competition is open to all of your fans, and not just your patrons, then that’s totally cool with Patreon. We just don’t want any competition limited to your patrons only as that implies they have to pay to enter.
That’s our policy, but you should also be aware of your own laws as they may or may not match our policies.
I answered a question about this more broadly here if you want some more context: Raffle Replacement
Happy to answer any other questions about this as well!