First and foremost, co-playing is forbidden, strictly by the rules. We tolerate it. Be happy we do and note that this discussion is not new. This has been in the rules for at least 10 years already and we're "tolerating" it for just as long. This won't change anytime soon.
Second of all, co-playing will remain tolerated this world. All you're unhappy about, as far as I read from your comment, is that you can't ask your future co to join separately and get an easy first few villages and outgrow your competition that way. Otherwise you would just let him join you straight away, which is still tolerated. Furthermore, "merges" are indicated by more than just a village switching ownership, which seems to be your misconception about merges.
It sounds to me like you're just sad there's no easy start-up for you anymore. However if there are other reasons hidden in your comment, please let me know so we can rethink the rule.