The latest attempt to add RBF to Bitcoin Core might cause unexpected delays in user experience by vendors waiting for (sender controlled opt-in) RBF. Would it be possible to modify RBF so that the transaction replacement is delayed? E.g. disregard replacement tx if the original tx has been in the mempool for less than six blocks. This way zero conf tx should not be affected, still stuck transactions could be fixed after some waiting time.

background: https://www.reddit.com/r/Bitcoin/comments/3ul1kb/peter_todds_rbf_replacebyfee_goes_against_one_of/