And for security risks, Ethereum has proposed a random sampling concept where authorized person will verify the block authentication. This can eliminate the trustlessness. What do you say?
Random validator might be able to give some degree of security but it won't give you the same security as a full node does.
I believe that's not the best solution if you want a blockchain for a decentralized currency. But for stuff like a smart contract or custom blockchain, it might be an alternative especially if the validators are known beforehand.