I think that many users of the TracBlogPlugin and SimpleBlogPlugin may be discouraged from switching based on the lack of an import tool. I personally feel that FullBlogPlugin is a much nicer tool with many features to offer. I personally plan on using FullBlogPlugin when I upgrade my server to 0.11 but I would also like to carry along my wiki blog post with out having to repost them all. So basically from my point of view, either a tool or documentation to help build a tool would be great.
Also while I've only been involved with Trac as a User, I'd be happy to help develop and test any tool. I am currently only using 0.11 as a testing system as we upgrade our website to use Trac as the main engine. So any testing won't currently affect my operations.