It would be great if Trojita could use an IMAP folder on my server to store drafts and more specifically: To edit and send them. Right now it only supports a local directory as drafts storage, which reduces interoperability with other IMAP clients, like KMail. KMail also supports a "send again" action on any email in any folder, which simply opens the message in the composer and allows to re-send it. This would be a good start, if implementing a special-case UI for certain folders and handling of RFC 6154 SPECIAL-USE mailboxes is a goal too far away.
Supporting at least the Trojita-produced drafts on the IMAP server and being able to re-read them is a nice goal, I agree. For other use cases, it might get a bit more difficult. We can do MIME parsing semi-reasonably, IMHO, but there's a lot of corner cases which did not have to be supported up to now. Patches welcome either way.
Trojitá is no longer maintained, please switch to a maintained alternative like https://apps.kde.org/kmail2/ Sorry for the inconveniences.