You would need a lot of IRL and 07GP to begin to fund and start something up effectively.
- advertisement on multiple platforms
- paying out winners
It is not a bad idea, it would generate a lot of demand for OS gold as a PoW value store, similar to crypto.
Iron is accurate in that you would need a lot of capital to weather variance and bad luck.
From a software perspective you would need a canned solution and some talent to integrate it and maintain it, specifically a node developer and a traditional sysadmin or cloud admin.
From a customer support perspective, you could get away with office hours support for processing deposits and withdrawals.
From a legal perspective, you could probably go underground since you will only be using 07gp, you don't need a financial structure.
IIRC some who have tried things like these have used web solutions, RuneStake or RuneBet I believe it was called. Crypto casinos have also been very popular, Seals with Clubs, Satoshi Dice.