PySide applies to 2014; in earlier versions, it is perhaps possible, but with issues. I really suggest that You looked into sample scripts available in PY documentation of MoBu. It is fair to say that without some wrapper classes, writing Your own GUI is rather annoying, complicated; I spent significant time wrapping everything into much easier to use classes, which allow me to design tools much faster - unless You design many toolboxes like I do, perhaps copypaste from samples may be Your best friend.
In v2015, I noticed they say they added PyGL, so that we might use openGL, too.
Also, look at fbmenumanager in samples - easiest menu is actually the popup menu that is generally shown after a right mouse button click in MoBu, so if You need just trivial Select Option choice, this is Your best friend potentially 🙂
Regards,
Stepan