Rewriting WP Plugin - the best?

I am considering switching my current scaled down ContentRewrite plugin for something more intellgent. ContentRewrite is fine for starters, but it doesn't support random synonims per word, and it's initial 1,2MB thesaurus produces absolutely unreadable text - had to scale it down to 1000 most used words in English and still it doesn't look good. So, what would you suggest? It has to be Wordpress, no way I am switching off to another platform.

Has anybody used Uniquefier? The idea seems pretty novel, but I'm guessing the search engines bots will just see garbage... so what its the point?