John Jack,
Greetings. Poser really is a great piece of software (I use it as well), but unfortunately the models are much too complex (too many polys) for use in a CG gaming environment. They certainly would cause the system to come crashing down if used within FPSC.
You could try exporting models as .3ds, and bringing them into a modeling program of your choice. Please realize that you will need to reduce the polys quite a bit, and the poser figures will need to be dramatically enlarged. You will need to rig and bone them for animation, etc. You could then export them as .x format files, which will load into FPSC.
Poser 1 models are the closest (though still too high) to a desired poly count for gameplay, that I seen native to Poser. Probably intentionally, for licensing reasons. Personally, I don't think Poser models hold up very well, as the geometries tend to "fall apart" and look quite crappy when exported to the .x format.
I hope this sheds a little light for you, and you might get some use out of this information. Please let me know if you find a "work-around" for this Poser-to-FPSC problem.
Thanks,
Seth Black
"...I'm sorry, could you repeat your question a little louder? I'm a trifle deaf in this ear."
- Willie Wonka