250+ fields sounds like there might be better ways to do what you want to do, but it would hard to be specific.
But one example. You mention that you’re going to have “Featured Blog Posts”. I would not create a box for choosing what blog posts to show. I would create a field group for blog posts that had a true/false field to set each blog post as featured or not. Then I would add code to the template to show blog posts that were set to featured using some criteria like the most recent 3 or 5 posts or whatever. I would probably also modify the admin list of posts and add a column to show if each post is featured or not to make it easy for the client to find the ones that are featured and edit them to change it.
As far as the rest goes, I would likely use Flexible Content for a lot of it and create layouts that meet the needs of their design. In fact, the “Featured Blog Posts” would likely be one of these layouts to let them choose some things about what “Featued Posts” to show. Or even, if the situation warranted, make it something that can be used for more than just featured posts, allowing them to adjust the content to suit their needs because with a little mortification it could be used for any realtionshp like “Related Posts”, “Related Pages”, etc.
