Hey Bryan,
Actually we are working on this. The next version will have an image and content parser options.
Once you migrate the content you have a parse content option that will go through all of the articles -> search for the images -> move them to the images folder.
In the content we are also going to remove the caption stuff, blockquotes, code etc.
<!--more--> will be replaced with the joomla equivalent so that you have proper intro and fulltexts. We are talking about the most basic stuff...
I don't think that it is a feasible challenge to fix all the possible combinations of formatting... At the end you will always need an editor to go trough the text and make sure that everything is ok...
Kind regards,
Daniel
P.S. next version is going to have user migration as well