That's an interesting thought. At first, I was thinking what you were suggesting would be very Tumblr-like, but Disqus would centralize your comments elsewhere, and maybe you could opt to pull a subset in to make your new platform?
The point is that there are probably 10 active commentators for each active blogger. Perhaps Disqus is building towards a platform for people like this, who comment actively but who don't want or think they wouldn't be able to run their own blog.