Really, they should just keep doing their own thing, no scanlator group owns the source material, they're each just making their own interpretation of it, and everyone is implicitly allowed to take the liberty to do so, unless the original author has anything to say about it.
Things started going wrong the second someone started acting like the license to make scans was sold exclusively to them.
Any respectable group would, if pressed, acknowledge that other versions can and do exist, but also maintain that they enjoy doing their own scans and do not think their work deserves to be discarded just because someone else released their version first. If not pressed, live and let live. I've seen a few gracious groups express appreciation that more people are making the effort to learn the language and produce scans, even if they've chosen the same project.
The scanlation communuty needs to stop thinking that it's right and proper "etiquette" to send other groups messages that amount to cease-and-desist letters. Not a single one of you unofficial translators have that right.