I understand why you're following 37signals' simplicity model, but those markets didn't have flexible CMS' to start with like we do. The beauty of WordPress is that it's easy to hide and remove extraneous features. It has everything you need and you can just remove the stuff you don't, just like the way a sculptor chisels away the unneeded parts. It's building from a different direction.
WordPress is a tool, not an end product, and it's been around for over 10 years.
Face it, websites are a commodity these days. What new features, processes, or anything else exist that WordPress can't do with a few tweaks? Front-end editing, one-click setup, drag and drop, it's all easier to add than building from scratch.
If your goal is to create value, then think hard about what problem your customer is trying to solve. If it requires something new, then by all means build it! But I don't see this as one of those cases.