My organization is interesting in that we have two styles of aikido taught in most schools. Anyway, a popular saying when we have our seminars (where we often invite teachers from other styles and orbs) is to "do what you see, not what you know." This isn't too difficult for a karate guy attempting aikido - but it can be easy for a Yoshinkan guy to do the version of a technique he is comfy with vice the ASU version being shown.
Thread relly - I haven't seen a book like that since my old karate organization, the GKK. I always thought they were neat, though. But when I interact with other dojo, I almost always wear a white belt and just tell them I am comfortable with any ukemi...I feel like a teacher at an unrelated dojo who would respect a rank book from another organization would be just as likely to take you on your word.
I have practiced several different styles of Aikido, Shorinji kempo, and a few kobudo and never had any problem adjusting. As you say, it is a matter of doing what you see and doing what you already know. Over the years I have invited many different Aikido shihan from different background. I find it interesting to see the many different approaches of Aikido. Aikido is a rich Art !