This is partialy what PP2014 GD is about.

it has the option to combine figures, and an extra option to lower the polgygon count of the combined figure.

Load your figure, drag-drop one or more conforming clothing item(s) over it, and click on "combine figures".
Now you have a single- clothed figure.

Then for Game or animation purposes, you can use the "reduce polygon" option to lower the polygon count to enhance the animation speed and / or the speed in Games.

Or?
Use Blender to combine the figure and the clothing items into a single object file. Depending on what items you are combining, you might have to edit the groups again.
Then edit a blank cr2 to point both paths in the cr2 to this new "combined" obj file.

Polygon count WILL change so the Original morphs will not work any more.
And you would need the "copy morphs from" function in Poser to get the morphs back into the combined figure.  

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Poser 1, 2, 3, 4, 5, 7, P8 and PPro2010, P9 and PP2012, P10 and PP2014 Game Dev
"Do not drive faster then your angel can fly"!