Why does everyone seem to want ninjas and world wars 1 or 2? Those are absolutely terrible ideas that have been done to death.
I personally don't think a female ancestor would be a good idea either, disregarding the whole Lara Croft ripoff thing it would look a bit odd if they made her face look like Desmond's as they had done with Altair and Ezio.
I personally don't think a female ancestor would be a good idea either, disregarding the whole Lara Croft ripoff thing it would look a bit odd if they made her face look like Desmond's as they had done with Altair and Ezio.