For starters, this function would return the string without the HTML tags:
jQuery.fn.stripTags = function () {
return this.replaceWith(this.html().replace(/<\/?[^>]+>/gi, ''));
};
Could you use jQuery or something similar to disable the ‘publish’ button until the word count is acceptable?
You would still need a fallback for those who do not use Javascript, but this may be a good solution to start with.