Eeeeehhhh... VisuStella obfuscates their plugins so you can't see the inner workings, and the problem is one of rewriting a function that they have almost certainly overridden already without breaking their functionality. I know that VisuStella is popular for MZ, but I'd be flying blind on this one. Things were so much easier with Yanfly, and he actually accommodated the text width return value...
Regarding the extra 10 MP cost, this plugin isn't really designed that way. It could be faked, though, by making three copies of the tripletech, each with itself as a component for one character with an extra 10 MP cost, and making sure each character learns the correct variant. Obnoxious? Sure, but writing that as a direct option wouldn't be trivial, and I haven't seen anyone else request such a feature.