we can do not only permanent bans, but also temporary bans

Having them making new accounts is better than having one of them getting to a high rating (specifically 1_2_3_4_5_9), ruin even the rating distribution of high ratings and inspire thousands of other people to cheat like them.

Alternatively, if somebody makes too many new accounts, he might get an IP ban, although I don't think it's necessary.

Don't ban people who only cheat one time. Only ban people who cheated for too many times (e.g. 3). Having consequent flags as a genuine coder is almost impossible. I did 23 contests and never got flagged for once.

Also we need a real appeal channel that isn't blog #8790.