Haven't read the whole thread, sort of started with the first post and then your's.
There’s first the point that NS disposed of much more time, and yet, tigers and lions can interbreed generating partially fertile offspring (apparently females are fertile, or so I've read), despite of the fact that jaguars, leopards and lions are more closely related with themselves than lions and tigers.
This is a very interesting fact on it's own. Can you speculate more on why they can interbreed despite being less related to jaguars and leopards, or maybe they can interbreed with leopards and jaguars too, but no one has tried to do that....maybe they would fight too much or something?
One could test the idea by impregnating them under medication....but cruel, but still, it would be interesting to see?