Is there something here?
Pretty much that. It was a finisher in a friend's landfall casual deck before it exploded in modern, could do the same for cube.
If you support the dark depths / thespian's stage combo it does something there too.
Scapeshift makes some of the retreats look really good (the red one gives +8/+0 at the very least, for example). I don't know that such a play is really conducive to an interesting match though.
I think it's worth testing at least. The bigger question to me is if the retreats are playable on their own. I might just make a land cube though...
360 lands, a box of basic creatures and utility spells draft?
Does the big bad Gitrog monster himself synergize appropriately? Draw 5-6 seems sweet.