I think if you simply realize that all stories are love stories nothing actually crosses. The object of the love may change ie love of another person, love of a child, love of a pet, love of money, love of fame, even love of power all are the same and all are vastly different.
I write what many may consider cross genre. My tales have their base in love of a man and a woman, however in each story one of the lead characters has the ability to change from fox to human or the other way around. I also throw in some Arthurian legend and some Catholicism. Now what you want to call that is up to you. I call it fantasy romance, not romantic fantasy which is something all together different.
As long as a story has impact it is valid. The problem results when you try to approach larger houses which function only on the bottom line. They buy what sells. Of course they don't often factor in that people buy what is for sale. As authors it is up to us to approach things in such a fashion that it matters not who is the publisher, but what the story says.