A couple of tips for making this dessert: be sure to cool the cakes so they come out of the pans easily, slice through each layer carefully for stress-free assembly, and beat the buttercream senseless. It took a long time for the frosting to come together, so just keep at it until everything comes together. It'll happen, I promise.
Can I please say that I'm just impressed with myself for putting this together? So often my desserts for company end up looking disastrous, or being underwhelming, but this was great!