RANDAO(n) I suspect is valuable, but it has a couple caveats that need to be ironed out before it can be included (plus, it needs an EIP champion to push it through).
Should n refer to block or slot? Slots can be empty (no RANDAO reveal), which makes block number appealing, but block number doesn’t have a well defined point in time in the future (which is useful in some contexts).
Regardless of whether you choose block or slot for n, at the least the block builder can choose between two options for that block. If a validator produces multiple blocks in a row, they get more attempts (combinatorial number I think).