This would be really useful. Horrid ol’ Wordpress has it as does Perch.
I am talking about being able to put a full blog post together with lots of picture and all, but on the blog page just show a snippet of this - size of which can be configured. Or do as WP does and have a separate field for the snippet so that what is displayed on the blog page is an excerpt of the actual post.
Also, I have just discovered that one cannot put a gallery tag into a blog post. Why is this? It would be useful for clients to be able to add a neat way to display pictures within a post.