If you enable psi-captures in the advanced options, you can MC a beast master at the end of a battle and get them in their armor that way. I don't know if Dioxine added stuff for the armored beast master, but when I did it in a previous playthrough, it was not as much of a breakthrough as I expected. Very little research is gained from getting an armored one, even though we all think something special will happen since it is difficult to do.