Speaking as a veteran of a blocklist project that was, i believe, run transparently and accountably, the following is my personal list of THE BARE FUCKING MINIMUM for any project to be considered adoptable by users.

• Blocklists should never be based on the personal blocklist of a person or server. No, not even as a "stopgap" measure. Start from scratch, period.
• While there will be some inevitable overlap (shitheads are seldom shitty in only one way), blocklists need to be topic-specific, and every topic list needs a clear mandate and mission statement.
• EVERY entry on EVERY topic list needs to be accompanied by receipts, viewable in an easy and convenient place. Not just reasons but ACTUAL RECEIPTS, in some archival form.
• At least three distinct people/entities must vote "yes" on a block before it gets propagated to any list, AND three or more "no" votes should be considered a veto of the addition.
• There must be a clear, formal appeals process, and that appeals process must also have multiple eyes on it (one person should not ever be The Decider of either a block or an appeal).
• Your project needs to have enough people on it to cover initial additions as well as reviews and appeals, and enough so that the same smaller teams aren't constantly in charge of those reviews and appeals. IMO that's at least 15-20 people.
• Block reversals (based on appeals as well as any other reason a block gets reversed) should be automatically propagated to users in the same way blocks are, if technically possible. Whether or not that can be accomplished, any reversals must be accompanied by actual public notifications that a block was in error/reversed on appeal/whatever. Those reversals should ALSO INCLUDE RECEIPTS.

Again, as far as i am concerned these are the fucking TABLE STAKES to do this kind of project responsibly.