is your hesitation to using nip51 list is just the score part?  what if the nip51 didn't include the scores just the list is named after a range of scores (top 1000 for example).  just thinking out loud here.. for my purposes I don't need the scores just the list of the pubkeys and currently can import from nip51 people lists.  I can also refresh the list, so say the top 1000 changes, I re-fetch that list and sync it.  (just like follows).  it also would be cool for clients to browse a feed from these lists.