I'd probably go with splitting by main character in the historical part. This is mostly because:
a) 1, the Ezio Trilogy and 3 are pretty different games, only really linked by Desmond
b) the modern main character in Unity/Syndicate is an unnamed "Initiate" who doesn't appear on screen and is presumably the player, and the modern MC in Origins/Odyssey is Layla (who appears for about 30 minutes combined over both games, if that) - linking Unity and Syndicate, and Origins and Odyssey, would feel really weird!
The questions I have are: how would people want to treat crossovers between games, and where would you nominate modern day ships?
Re: Assassin's Creed
a) 1, the Ezio Trilogy and 3 are pretty different games, only really linked by Desmond
b) the modern main character in Unity/Syndicate is an unnamed "Initiate" who doesn't appear on screen and is presumably the player, and the modern MC in Origins/Odyssey is Layla (who appears for about 30 minutes combined over both games, if that) - linking Unity and Syndicate, and Origins and Odyssey, would feel really weird!
The questions I have are: how would people want to treat crossovers between games, and where would you nominate modern day ships?