I would love to have a new torrent feature: DripFeed.
I would like the rare torrents to get priority, both In and Outbound.
All of the busy torrents can have my help after the rare stuff.
I suspect this might require signalling the each torrent's mode, to avoid problematic scenarios of 10k (not rare) torrents yet 0 were shared (because it was too "popular").
If I recall correctly, eMule used to have something like this, but I haven't used that for years.
If this feature exists or can be configured, I'd love to hear about it.