This actually gets rid of unnecessary triangulation, while keeping any triangulated non-planar faces split up, but it uses Booleans and I know some people have a lot of trouble with those. If your object already has a heirarchy, i.e. debris, turrets, lods etc, take it apart. This will mess things up big time if you don't, as booleans don't really know what to do with subobjects. Next, create a cube (small is fine, big is also ok) and place it where it doesn't intersect or touch your model at all. Next, select the object that you want to detriangulate, and boolean union it with the cube (make sure your boolean operations are set to delete edges, this property can be accessed by right-clicking the boolean tool). Finally, take the delete face tool and remove all six faces from the cube so all that you have left is the original object. You'll have to do this for each object that you have, but it is the only fast-and-nasty way of detriangulating a model that I am aware of. It keeps UV mapping intact as long as comined polys were in the same UV map group, so it shouldn't do anything negative to your model other than forcing you to rebuild the model heirarchy.
