The Lockout Championship recently ended and it was a lot of fun watching the best of Codeforces compete with each other 1v1 and that got me thinking, Why not have a feature here on Codeforces where people can create a 1v1 challenge (or duel) and compete whenever they want (as opposed to contests)?
People can create a challenge, which would consist of problems from past Codeforces rounds. They can set the number of problems, the time control (total or per problem), the difficulty range, the order (random or sorted) of problems by difficulty, rating range of acceptors, etc. and others can simply check out the lobby and accept the challenge that best suits them. Those who play chess on sites like chess.com or lichess.org would know all about how these work.
We could have a separate "duel rating" for the handles so that the duels don't mess with people's contest ratings.
I am sure it would be a great alternative to the regular format of div1/div2 contests that we all know and love. Since there are editorials for the contest problems and people can use them to cheat in the duels, we could hide the problem details pertaining to the contest to which they belong and only show the problem statement, I/O, and sample cases in duel mode.
So...what do you think? Any Ideas?