Modern Grammar checkers have gotten halfway decent, they'll catch the obvious " your you're" mistakes.
I'm suggesting a new type of computational grammar checker that also checks for tone and lazy writing. This doesn't take as much logic as one would suspect.
by using "black-lists" of so called
lazy descriptors, weak-verbs etc it can guess to the tone and talent of writing. if you keep on using "like" in 10% of sentences it will notify you and suggest changes. Like wise for using the passive voice, or other common writing faux pas .
This can be enhanced by using so called "standard" documents notable papers written with good grammar and character, by examining average word length, sentence length number of adjectives and several other metrics you can have the computer highlight areas that could use some sprucing up, or even make the edits for you. Think of it as an auto thesaurus. Now if you want to write a very harshly worded letter simply load up examples of youtube comments and I'm sure your paper will be bound with colourful prose. If you want to sound technical load up white papers etc and compare your grammar to theirs.
** when I find the link I'll post it, a similar program has been developed for music which matches a recording of a master musician playing a piano to the written score, to attempt to analyze how the maestro interprets the score. I'm suggesting a similar thing for writing which takes a master authors tone and imparts it onto the dull writings of the everyman.