I built a similar plugin a year ago: Disable Blog, and I'm currently working on final tests on the next version (0.4.0).

My method was to redirect in most cases, either redirect admin pages to the dashboard or front-end pages to the home page. Other blog-related things are either hidden, disabled, or redirected - no database changes. Filters and action hooks allow for more fine-tuning of the plugin as well.

I don't think unilaterally disabling everything remotely related to the blog features is necessarily correct, and I've endeavored to allow custom post type and custom taxonomy support so developers can build public-facing custom post types, but still have the built-in "blog" functionality disabled.

For instance, XML-RPC can be used for things outside of the 'post' type, and comments should be available and active for pages (there's a good plugin for disabling comments already out there). Same goes for pingbacks, trackbacks, feeds, and even categories/tags (if they are used in another post type).

Not sure how the user profile fields being simplified is related either. I'd argue that those fields can be used in the context of pages and/or custom post types, depending on the theme's author template.

If anyone would like to see/test/contribute, see the github repo. Thanks!