vB5 uses CKEditor which can be customized by adding plugins. But vB5 makes it hard to easily install the plugins to CKEditor without hacking the existing ckeditor JS files. I've never done what you're asking for but as long as appropriate plugins are available for what you need then it's possible to add them to vB5 editor.
I've done other ckeditor stuff. For example, adding a new font:
http://vbmods.rocks/forum/vbulletin-...lletin-5?p=595