Need help extending textarea fieldtype

Please see original thread in old forum for reference. Essentially, I need to create a new fieldtype that extends the default textarea fieldtype (/perch/core/lib/PerchForm.class.php line ~910) to run htmlspecialchars() on the $value before CKEditor is loaded on an edit page in Perch. In the original thread, I feel that Drew is hinting that this shouldn't be too difficult, however I don't know enough about PHP to even know where to begin.

I have so many use cases and requests from clients that could easily be solved with CKE plugins. If anyone can point me in the right direction, I would greatly appreciate it and would be willing to compensate your time. I imagine I'm not the only developer who would benefit from the ability to add CKE plugins to Perch.