Going back to the morph discussion, the only morph I'm currently running is
Grim Haruspex, and I kind of wish I could just erase the morph line from it because I love the effect, and literally the only other creature with the ability is
Harvester of Souls which is too expensive.
I've been aware of keyword complexity for a while. It's the reason I don't run
Greater Gargadon despite how good it'd be in the RB sacrifice deck, because suspend is a super weird keyword and it would be the only instance of it in the cube. Gargadon doesn't even have reminder text! For a while I refused to include any card with a keyword unless I could fit at least 3 cards in with that keyword. I've relaxed that restriction along the way, but the basic idea still informs a lot of my decisions.
As far as double-faced cards go, I think they're super easy to grok, and I think the idea of them is actually pretty elegant. I just don't include them because I draft exclusively in paper Magic, and I don't like the physical logistics of pulling the card out of the sleeve and flipping it around (there was a point when we were drafting in bars and cards got damaged). I could include checklist cards, but that once again gets into comprehension issues for drafting. I had a guy who'd literally drafted once in his life drafting my cube on Wednesday. He was lost enough as it was without including that kind of thing.