Re: Mixing Aikido with other martial arts
Nope. Definitely haven't seen that where I train. But I have seen something similar to what you mention somewhere I used to train. It was when the UFC first came out...I remember a bunch of students standing around discussing how they felt the Sensei would fair...it seemed a bit idealistic at the time...more like a pipe dream now.
In most of the places I am familiar with now, that kind of idealism/naivete would simply draw some rather strange looks, and perhaps get you pulled aside for some much needed coaching on what Budo is and is not.