[FairyKing]

I have a theory with no evidence to support it, but I think it sounds cool so I'm gonna say it anyway:

Like W, Build's design is asymmetrical because he's a two-in-one Rider, two people coming together to "build" a hero greater than the sum of his parts. But what makes this series more than just a rehash of W is that it's not always the same two people. There's probably one main protagonist who wears the driver and forms the basic body, and then each member of the supporting cast has their own henshin device (the little bottle things) that they use to "build" onto the Rider as extra armor and equipment, with each partner granting Build a different form, and the final form would most likely be achieved by "building" with all his allies at once.

Just an idea that popped into my head looking at the asymmetrical silhouettes.