Several years ago I started something similar. The idea was to create cloze test flashcards. That never really took off, but some teachers liked the general idea so I rewrote it to become a cloze quiz creator tool which is now http://www.learnclick.com (it now offers much more than cloze quizzes). Congratulations Mike for coming up with something for the individual learner. I think having premade cloze sentences was what was missing with my original solution.