hmmm... how much of another style is required? I hate to say it but I see another sort of can of worms here...
Do you learn the basics of a style? So for example if you learned Yellow and Orange and Purple belt curriculum in a Parker Kenpo lineage, would that be enough? If so, does that merit a jump in Dan Grade in your organization? Or do you need to advance to shodan level in the second style, and that is given a dan grade jump in your org?
Learning any style can be a lifetime endeavor. I personally find it unusual to use that as a ranking requirement for an organization.
more enlightenment, if you will?
In my old dojo, it was required that you earn at least shodan in another style before meeting any of the other qualifications for 5th dan.
I will say again that this is not required of me through KFCI, but I think it would broaden the scope of my experience.