We have run lines from the rear remote to the front for the third function for years. Not quite as nice as being nearly all steel lines like the factory units on the 660 series but functional.
I won't be hitting the dealers 'till next summer, but when I figure out what can and can't be done I'll report back. My being a newbie is going to show with this next question - Don't you need a 3rd function remote to run a grapple?