Let's PAR the night together

More files are appearing without PAR (or PAR2) sets. Or with PAR sets that cover a number of discrete items. Traditionally, it has been the responsibility of the OP to provide PAR sets, but I wonder if it's time for automated PAR generation, perhaps as a low-cost feature of an existing access provider, a way to avail processor cycles during slow times of day.
The request could include a pointer to the file being rehydrated. If that object is another PAR set, then the request is for further PAR's in the same set. It might also include a measure of how many PAR blocks are being requested. Unless already known, the size of a block for these purposes would need to be standardized. Finally, there might need to be a scrambled-looking name for the resulting PAR file. I don't know, could there be legal repercussions for the access provider? Or should I say, additional legal repercussions?
Sorry if this is a noob sort of suggestion, I did attempt to research and did not find anything pertinent.

I've noticed that too. Sometimes the RARs contain a recovery record (which will fix minor issues). If someone downloads an archive without PARs and it comes down good, they could then create PARs for the RAR files and post them. If there is an issue with the original archive and no recovery record was included or it won't repair archive, SOL.

can't see this happening automatically, its just giving work to servers. It would have legal implications too, at the moment they have a deniability especially if they have a take down policy, post par2 to a file that then gets a takedown would open them up to claims of having knowledge about the files if they have added content since the Par2 would be part of the takedown.

The question is why have you incompletes? If its the original poster did not fully upload, then any auto par2 wouldn't help. If its because the server you use has blocks missing, e.g. rather than age/group the server did not grab a complete copy etc then the argument is to get a back-up server subscription. There is, somewhere, a map of the various news providers connections of where they get posts from, which is good for selecting a back-up provider since you need to get one that uses a different source. That way if posts are incomplete on one server you can re-download from the back-up (if your back-up is a branch from the same root then its likely if your primary is incomplete then your back up could well have the same incomplete)

Sometimes the PARs get posted separately from the RARs. Maybe some posters don't know about PARs or how to use them. For small archives the built-in RAR recovery should work fine (unless a file is missing or incomplete too much). WinRAR can create its own recovery files (separate from RAR archive).