First question would be if there's a NIP for that. Obviously it's up to relayers and clients to actually delete it, so such a feature might give a false sense of security.
Discussion
NIP 9 and NIP 40 allows clients to request deletion of events. Relays delete them most of the times. Not looking for security but to avoid manual deletion of events after shitposting. A user could enable expiry, shitpost for a few hours and forget it.