@Oeconomist
Framing it as "lowering the cost to leave" is the wrong way to look at it I think. It assumes the end-goal is to make scanlation groups as dependant upon Mangadex as possible, just to keep them on this site, and if they weren't dependant there would just be a mass exodus.
This is not the case, as it is now Mangadex is far more dependant upon scanlators posting here than the other way around. Scanlators largely post here in order to reach a wider audience and, in most cases, it's far from the only place they post their chapters (not counting the stealing that's going on as well), or in some it's simply that they don't have upload restrictions and they don't upload here in person at all, it's just users doing other users a favour.
Giving scanlators some more tools to control their releases and promote their own sites will therefore not necessarily mean they will go for a rip and run strategy of never upload their chapters here any more. As it is everyone is already plugging their various discords, patreons and whatnot; clickthrough rate not withstanding. Providing more direct links to the various' groups portals might alleviate the need for the group delays, which is partly the cause of this drama.
Moreover, that strategy wouldn't be that bad from Mangadex' perspective. Even if groups would only upload credit pages or links informing people of a new chapters, Mangadex would still fulfil it's hub role and people would still visit Mangadex' site foremost to get their updates. This model works well enough for NovelUpdates, so I don't see why it couldn't work for Mangadex.
That said, Mangadex
does provide a nice uniform reading (and uploading) experience and if anything I think more and more groups will upload here foremost, if only to avoid the hassle of having to host an online reader themselves.
Lastly, discussing rejected proposals isn't necessarily redundant. Obviously it shouldn't be done immediately or all the time, but some proposals can and should be re-evaluated because they turn out to be decent proposals after all or because circumstances changed.