It would be cool to have a server option that would use that server as a last resort.
Meaning that for a Rar+Par posted set, don't go looking for posts on a server until Newsbin has downloaded all Rar and Par segments it can get.
This would be different than simple server priority.
Server with priority 1 - Main server, holes sometimes
Server with priority 2 - Slow, can fill in most holes
At this point it would be better to recover holes using pars than to try and download them from the "last resort" server. This would use the absolute minimum from a block account.
However I don't want Newsbin to always download pars first and repair as soon as it gets enough parts. Par recovery takes a lot of CPU compared to downloading.
This "last resort" only accounts for about 5% of the download cases (for me at least). I've been doing this manually.