Natalie -- don't torture yourself about this.
My favorite thing about your style is that you make hyper matchy and theme dressing pretty, interesting, fun, and quite fashionable. Ironically enough I would not describe your persona as whimsy though your approach is decidedly whimsy.
Your mind map of outfits focuses on themes and whether items echo each others' patterns. This is a unique and fascinating approach to outfit making. I am sure if I let you loose in my closet you could pull together fabulous outfits I've never dreamed existed simply because of your approach. I am sure you already have capsules centered around what to wear for Halloween and what print matches that skirt with the tree branches on it

I totally missed this before, but the first thing that came to mind is that you already have many very small capsules deriving from your great love of matching. You have a black/white print capsule, a Scarlet red capsule, an ink blue capsule, your orange slice themed capsule... this includes your shoes and jewelry since you have some awesome thematic pieces. And some pieces definitely cross over for sure.

In my mind matching and mixing are opposing forces, so you need more, smaller capsules than others.

Thanks everyone for such great insights! It's true that I'm so into themes and hyper-matching that it makes it hard to do a mix and match capsule. (Rae, I love your description of my "orange slice capsule". Now THAT is a capsule I can get on board with!) Plus I'm kind of a perfectionist and would want every item in the capsule to work with every other item, so that makes it tough. Although Angie is right, making a capsule is a very useful exercise for analyzing your wardrobe. I just bought a few casual items at Gap including a pair of camo jeans and a denim moto jacket, so I am actually excited to try coming up with a casual MOTG capsule when I get a little time to play around. Thanks again everyone for all the wonderful comments!