This is pretty cool! Had a similar idea for nostr:nprofile1qyt8wumn8ghj7ct4w35zumn0wd68yvfwvdhk6tcpz9mhxue69uhkummnw3ezuamfdejj7qpqqf9pur8yz8e8w78ap6255fx9x6xrakm2jgmqyv063l9365p7sdcs7adyk5 but never got around to implementing it. Here are some of the design sketches in case they are useful.

Seems like the main difference was that in the case of pubpay the bet events would be kind 1 with special tags, and you'd have the ability to determine other kind 0's witnesses to validate the results.