Using "stable" releases of dolphin isn't going to work at all as is. 3.5 was released 2 years and 900+ commits after 3.0, and we are now almost 1500 commits past 3.5 in the last 7 months, and still quite a ways away from 4.0. Dolphin is under fairly heavy development, and releases just are not done anywhere near often enough.
Finding builds for older dev builds isn't really a problem in this case either. Builds for basically every single revision ever can be found at
http://dl.dolphin-emu.org/oldbuilds/ or
http://dolphin-emu.org/download/ . Every single commit, including to branches is built automatically, and available at
http://dolphin-emu.org/download/dev/[hash]. In recent revisions, the hash is saved to the movie file. For older ones, it's right in the about menu.
Of course we could always fork it and do releases separately. But who would be willing to do that? You suggested rog on irc, but he actually did move to an uninhabited island, never to return, months ago. I could do it, but i don't really think it's a big deal as is. There's not many people tasing dolphin, and in most cases (of course there's two exceptions on the workbench right now...) builds are easily available at
http://dolphin-emu.org, and the source is just as easy to find. Obviously it's a still a headache that doesn't exist for any other emulator, but I'm not sure what can realistically be done about it that wouldn't be just as much if not more of a headache. I'm not really interested in maintaining a fork to be released every few weeks that will mostly go unused, and i doubt anyone else is either.
