You can build clothes in quadrangles from the start. It's an option in most 3D modelers. To convert, you can either use a 3D modeler, or a little script named "detriang" in the freestuff, by Anthony Appleyard. Of course, you lose the morphs (and may be the mapping ?), but in the case of 3Dtrue's suit there were neither. As for P4 cartoon w/line, I don't use it. The toon shaders are much more versatile (let you use procedural textures, trans, texture maps, bump, displacement...). It speeds up the process to just make a render and you're done. For the rest, postworking can do wonders.