i think the way to chose to add file paths to the archive could be improved.
for example you can either add the whole path to a zip archive or no paths at all. relative paths would be nice too...
you can not chose if you want to add file paths when using the thunar archive plugin either.

so here's my suggestion:
let the user chose in the "new" dialog via a combobox if he wants to add absolute, relative or no paths to the archive. this way it could be used correctly in the archive plugin.
save the chosen state and use it for the "add" dialogs. so if a user wants to add files to an archive by himself, he doesn't have to change the way of how file paths are added again, but he _could_. i suggest using the same combobox in the "add" dialog if the archive type supports file paths.

when using the "add" dialog but not have used the "new" dialog before, use a sane default like relative filepaths.