Mechanics I've seen to avoid this:
- Occasional sitewide freeleech
- bonus points for seeding duration irregardless of upload, can be traded for reducing download
- freeleech torrents (only counts upload not download)
- partial freeleech (25/50/75% download counted)
- Timed freeleech (free first 24h)
- Download % counted reduced based on seed size (seed >1tb and everything's freeleech)
- Reduction of download % counted based on rank
- Forum competitions for bonus points/freeleech tokens
- Freeleech tokens giveouts
Hell, there's quite a few PT's that don't care about ratio and just have minimum seeding times on torrents.
Plenty of these trackers have been running 1-2 decades on 1 or more of these methods just fine.
Almost every site is laughably easy to keep ratio if you read the rules/FAQ, look at some what's to build points/ratio, read the forums, and don't go nuts In the first week while your establishing your account