To my knowledge RF can't mix animations like that.
However, I once played around with this thing. I had a model with complete skeleton. Then I took the skeleton and put it in half, in two parts. One part was the upper body (head, arms, chest) and the other was legs. Then I made animations for the legs and the upper body seperately. Note that I had only one model, I divided the skeleton only! I hope you get what I mean.
So the model (.bdy file) had a complete skeleton, but the animations (.mot files) were missing bones. The leg animations didn't have upper body bones and vice versa.
I found out that if you play a 'leg animation' for the actor, the upper body freezes to the position where it last was. So, what I'm trying to explain here is that if an animation file is missing certain bones, those bones don't go to their default position when the animation is played, they stay right there where they are.
I put my pawns in pretty interesting poses that way. For example, imagine a soldier doing a roundhouse kick and when the kick is halfway delivered, the feet freeze and he draws a pistol and starts shooting. It was, well... weird to say the least!
Too bad this can't practically be used because RF can play only one animation at a time. I wish RF could play more animations for one actor, it would allow us to do those mixed animations.