Well, it doesn't (shouldn't?) cost anything to start up a blog, right? So, if you think you see a need, go ahead and give your blog a try!
I agree with carnation that focusing on very rare circumstances, such as having a stoma, would net a very low readership. The chances of having a reader who falls into this category is extremely slim. However, the concept of including a PNM audience generally grouped as "women with additional considerations" (medical device, wheelchair, crutches, severe acne, etc) could make them feel included and be a viable topic for a blog post.
The other ideas for including different body types, ethnicities and locations (ie. winter wear for a northeast spring recruitment) could be helpful too. I've been out of the game for a very long time, but a lot of the blogs I've run across seem to be of the blond, Lilly-wearing, Southern girl type.
Again, the blog could be worth a try - your readers are the ones who will ultimately decide if it's a winner or not!
