TinyMce/Editor on custom textarea

I think you're going to have a hard time trying to build a custom editor that works just like the OOB editors.

The problem is when community loads the OOB editors, it grabs specific configs for that editor from the backend (so the blog editor might have a different backend config from the TKB editor). It also takes into consideration the users HTML permissions to determine which editor tools to load.

If you're creating the editor on a page that already has an editor, you might have slightly better luck trying to duplicate.