One suggestion: a minimum bid amount unit. I was bidding for a site recently in another thread (private auction a al SBI’s effort), and was told that my bid wasn’t significantly different (it was $1 or $5 -forget which- more than the previous bid).
But the terms of THAT auction did not specify a minimum amount, I definitely felt cheated, I would have offered a higher bid than that. But I felt that a significant omission in the auction process left the impression that that process lacked integrity.