The Juki TL98Q has been my "dream machine" for a couple of years now, and I'm happy to learn what I can about them from users. It looks like a wonderful quilting machine--I have a photo of one on my workroom wall that's being used on a quilting frame. I'm really happy with the Juki 4-thread overlock that I bought used 20 years ago, so I consider the TL98Q a once-in-a-lifetime purchase.
Even with a Sidewinder bobbin-threader, you'd still have to stop work to install it, wouldn't you? Ha. I should go read the manual!