I just want to make it clear that if you adapt a plugin in this manner, you would essentially fork it under a new name, except it's not published. Don't hack up a plugin then try to update it! You'll lose all of your custom code.
Ross' summary is so succinct and accurate I would suggest you piece together your own code based on it and take examples from other plugins and code snippets as needed rather than trying to find the closest plugin to your needs. I think it's easier to find elements that do what you want than entire plugins.
IMHO of course, do what works best for you.