The PolyCombine plugin for trueSpace will act on a selected hierarchical object(a glued object) and create a single polygon mesh copy.  The copy will inherit the original's uv space, materials and axes.  It can be used to prepare a model for export to an Unreal static mesh using the ASE export plugin.  It was written for trueSpace 6, but it should work with gameSpace and trueSpace 5.
The image above shows 2 triangulated objects.  The one on the left was boolean unioned before triangulation.  The one on the right was polycombined before triangulation.  Both objects are each composed of a single mesh.
The first step is to glue all the meshes together.  The plugin will work with hierarchies composed of 2 or more polygon objects.  After everything is glued together, click the PolyCombine icon and a single mesh copy will be created.
Click this line to download the PolyCombine.tsx	The source code is available at the bottom of the page.
The images below compare the PolyCombiner to the built in boolean functions.
PolyCombine	Union
Subtract	Intersection

Click this line to download the C source code