Currently, the only options for duel requests are to have them disabled altogether or enabled for everyone. It would be a nice QOL addition that I'm sure plenty of people would appreciate. For example, I don't like having my duel requests opened because I get to many just random ones from random people, but say one day I want to do a duel with a custom kit with @Spoon to show how bad he is, I would have to enable them before and then disable them after, or I would have to keep them enabled for my entire life, which would result in me getting loads of unwanted requests.