The more I think of my rating system the more I realize that there would need to be a limit on the number of variables. (Sorry, programming term!)
Basically, the more info a rating system keeps track of, the more load on the server ... the more info that needs to be loaded by your browser.
So, a limit on the number of variables while still providing informative feedback would be in order. For example, instead of having a seperate rating for commas and periods, have one rating for punctuation. In each category limit the number of sub-categories to about 5. So, in the end, a piece of work is rated based upon 15 items: 5 grammar items, 5 content items, and 5 possible entertainability items.