Main issue with doing this sort of thing in Poser is that it doesn't have the rigs to do it. This is what a student level (but fully capable) rig looks like in Maya, for example:

https://www.youtube.com/watch?v=h3YKuj6qjAM&feature=emb_logo

Now try doing some of that in Poser with the rigs you have in various figures. The issues will become self evident to you.