You can already add your own additional attributes (including epub:type and role) via the config dialog. Adding additional tags is a tiny bit more involved, but I tried to make it as simple as possible (two changes in the utilities.py file)--mainly because I got tired of all the requests for additional tags/attributes!
All customizations will survive uninstalls/upgrades provided the preferences json is not manually removed.
The config dialog is available via the "Edit" menu item, in case you hadn't noticed it.