Futaba vs. JR
There are issues with using a Futaba / BrandX combo in buddy mode. I recently set up a buddy between my 9Z and a 4ch Hitec... what a nightmare. I won't even begin to explain the hurdles I had to jump to get that to work. However, one really can't expect Futaba to be compatible with other radio brands. Futaba is HUGE compared to other brands, if anything, the other brands should have an incentive to be compatible with Futaba, not the other way around.
As for Futaba/Futaba buddy systems, I've never seen one as powerful as a 9Z to 9Z. Miles above anything else I have ever seen. SteveC just barely touched on what you can do with a 9Z buddy system.