Hi Thanks for your email:

• We'd welcome assistance with developing the Editor, so long as developments could be released within CodeCogs. I like your ideas, however understanding physically how to achieve this is not trivial. If you use Mathjax to render the equation, then this creates possibilities because its pure HTML and therefore you can inject code to allow the user to select parts from the rendered equation. However, I think a different route use SVGs might work just as well. Using SVGWeb its essentially supported by all browsers. The main advantage of an SVG route of Mathjax is that its very portable, it give you complete control over the formatting and most importantly it doesn't require any javascript libraries to be installed to display.
• We'll shortly add an option within the editor that uses Mathjax to show the output. Its a good intermediate tool that we support.
• We're working on a plugin for CKEditor now. Hope to have a page ready in a day or two explaining the integration with examples.