Don't be so sure. My Light Brahma LF roo has taken a REAL liking to a gold laced bantam cochin I have. When I first saw him "dance" and then breed her I was shocked and amazed that he did not hurt her and that she didn't run for the hills to boot - I would have. He is at least 5 times her size. He is very gentle with her. Now his 4 light brahma hens he basicly grabs and mounts whenever he wants. He romances the little bantam hen by dancing and struting in front of her first and she always submits before he even trys to mount her. I have one egg from this pair that I just set in the incubator the other day - hoping it hatches so I can see the results, lol. Should be interesting!
Personally, I would not want a rooster that was not the same breed as my hens. When the hens got older and needed to be replaced, I would not want to take a chance on what kind of chickens I'd end up with when I hatched the crossed eggs. I bought the breed that I like and wanted to stick with because of their temperament.