I'm not technically inclined, however I think you're first to discuss this AFAIK. But I feel like if this is not just for testing sake it will definitely not be a good idea because whatever has to do with the internet and saving private keys it's very much the opposite of each other, which means the risk of it getting compromised is very high.

I do want to believe you're just proposing this idea for testing knowledge, so I will ask if you try this out eventually wouldn't someone with high tech knowledge be able to brute force the private key? even with the way you proposed it under op_return.