I like the flip top bar top suggested, but if you had the freezer on wheels, and the tower mounted to the bar, depending on the clearance between the bottom of the bar top and the top of the freezer, your lines can live in your freezer and go through a hole on the lid straight into the tower. The lines will need to be in the 12-15 foot length to balance the system and overcome the height....so as long as you can guide them back into the freezer when you slide the freezer back into place, it all sounds workable.
Or, do the standard collar and have them under the bar....not fancy, but practical.