>I briefly considered writing reports to (say) PDF files on the host and then somehow getting those files to the remote users, but that would be extra complication for no real gain.

That was first idea that popped up and if user info can be coupled with email adress probably in long term one of the best maintainance saving options. Even if users have to download after being mailed a DL link, on the users side you are isolated pretty good from OS update harm.