If you can physically do it (ie. your side stays actually let you) it's a very good idea and used a lot on your average racing yachts. Since you've not posted any pics of your side decks, it would help to know what sort of boat you have.
You don't need extra lines
in the cockpit - it's only the track you need to install. You move your existing jib
cars and sheets to the inside track whenever you intend to use it.