Reporting back!
The short of it: The pineapple upside down cake was a success, and loved by all! It's likely I won't make it again, not because it was difficult, or wasn't good, but pineapple just isn't really my favorite. I really enjoyed the frosting - subtley pineapply, tangy, and not too sweet. The poached pineapples pair with the crunchy crumbs really well. I'm glad a friend who like a type of cake I'm not super into has a birthday so I could try a recipe I likely would have skipped over, or just picked and chose components of.
One thing I would have liked was some sorta of toasty caramelizey component. When I think of PUD, I think pineapple, maraschinos, and that cooked sugar on top. There wasn't really anything to pick up that warm sugary flavor.
The long of it: I swapped out the coconut cake for my favorite vanilla cake recipe. There's a vegan vanilla cake recipe in the back of the book, but I decided to forgo it so at least one component of this thing I'd never made before and was serving to people for the first time without trying it was tried and true.
The cake soak is great - although, I swapped out the milk and buttermilk for equal volume of coconut milk and teensy squeeze of lemon juice. The coconut milk worked extremely well. 10/10 will soak again.
The cake crumbs - if you're not down with cake mix + butter, I'm not down with you.
The poached pineapple - scented the house amazingly. Two cardamom pods was the perfect amount to just get that warm from the pods, and not a whole pile of flavor.
The frosting - is an emulsion! It's turns out super smooth and soft, so not pipable by any means (but why would her frostings be), but it's really really good. Not too sweet, subtley pineapply, a little tangy from the citric acid. The cake mix wasn't as huge a part of the flavor as I had though it would be, but it got the pineapple + cake thing across. I'm an American buttercream girl, so this was an interesting change to what I'm used to.
Caveat: All recipes are veganized (aka, I use Earth Balance instead of butter, coconut milk instead of milk and buttermilk, and accidentally vegan cake mix in this recipe).