Maybe I am missing the whole idea here. But all of the DE's are Gnome 3 based, correct? Cinnamon, MATE, and MGSE?
MATE is maintained by a different group than Linux Mint, and can be used on other distributions.
Cinnamon and MGSE are the two interfaces that Mint maintains. And if one is to be dropped in favor of the other, I would say to go with Cinnamon instead, as it and MGSE are very similar, and Cinnamon is obviously the next evelution of MGSE.
Mint, unlike Ubuntu, doesn't limit itself to a 700meg CD, and could include MATE, Cinnamon, and Gnome 3 Shell. I know that with Mint Lisa 12, the package (download) size of Cinnamon is only ~15 megs. And all of the above are built on Gnome 3, so that is going to be included by default.
The main reason I switched to Mint from Ubuntu is because of the better interface, I prefer Standard Gnome 3 Shell, MGSE, and Cinnamon over Unity. That and Clem seems to listen to his users, and is building an interface that we all want and like. I believe this is why Mint has over doubled the hits on distrowatch.com over Ubuntu.
Anyway, I personally think that MGSE and Cinnamon are soon to be the same interface, and that MATE is something people like, and all of which are built on Gnome-3. So, why not include Cinnamon, MATE and Gnome-Shell on the ISO image? Heck, you could allow the user to pick a (default) interface during install. The other two would be installed, of course, and could be selected at any time... we all like to play with new interfaces from time to time.
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