Is Irdeto harassing you with DMCAs or just the hacking / forum spam complaints?
I am thankful that I have my own AS and IP space. I would even think about running mass relays like I do. I am running the reduced exit policy on all 50 of my relays and still get tons of automated stuff like you spoke about.
Now, If you leave all ports open like Conrad and I do on most of our relays, a copyright enforcement company called Irdeto USA (the same
replies, and contact upstreams directly rather than the contact on the SWIP Record - be rich and get your own ASN to get around this. Now, Irdeto's business strategy is a simple one they need only to flood your ISP's abuse department with as many automated DMCA Emails as possible until they get too many to ever hope to respond to and then try to get them to terminate your account. Depending on the ISP it'll work.
Own AS helps as with SWIP... you look like a biz / isp... the upper tiers are less likely to cut your connection unless bill unpaid, though you're hardly likely to actually be peering with them, so you're still somewhat subject to the smaller ISP FUD game. ISP meetups in every city, make friends.
Automated? Waste of time, filter into archive and ignore. Copied to upstream? Same unless relationship says otherwise. Handwritten? Stuff with a hello back and a Here's Tor template. Get cracked? Say thank you.
For the most part, it's all a game... bluster, corp i-dot t-cross fud, and whack a mole. Rarely to court in jurisdiction, which will happen or not no matter how you process mail. Simple incorporation filing solves that, fold in civil and reboot, unless jurisdiction is insane, for which you'd be insane to risk criminal jail to operate there non structured / defended / anon. Book counsel and plan before deploying. Or fight, isp rarely lose speech / proxy anyway.
Irdeto bittorrent and all others can go spin... https://www.techspot.com/news/76190-us-court-appeals-ip-address-isnt-enough-... http://cdn.ca9.uscourts.gov/datastore/opinions/2018/08/27/17-35041.pdf
Generally, automatia is noise to cancel, bluster back at fud threats with well collated set of links / info / education, maybe they end up converting using overlays and crypto lol, thank the occaisional helpful human, etc.
No best answer.