When a unit has several talk animations, it is usually better to make a separate portrait model.
Using or modding one is easy, but making one from the ground up from the main model is not easy, unless someone knows an easy way... I am not experienced enough yet to make my own custom complex animations, all I can do are simple translations and rotations.
This said there might be some tools around to help making these custom animations, unfortunately I can't help there as I have never used such a tool.