I'm looking into developing a webcomic publishing plugin for Wordpress.
ComicPress exists, but it's complicated and forces you to use a theme. I
want to make something simpler that lets you use any kind of theme.
What do you guys think?

Sneaky
I don't know much about either but it may pay for you to see what others are doing in a similar vain.

There are a few of them out there already, ComicPress and Inkblot I think are the most popular. I didn't think they FORCED you to use a theme, as much as there's a default and you can edit it if you know how? It might be worth finding out what people do and don't like about the already existing plugins and seeing if you can improve on them.