a different bike, but i have a pic of it i can get to, and it has the start of the same set up.
https://www.facebook.com/photo.php?f...type=3&theater
3sp trike hub where the two chains meet, and a 5sp shimano front freewheel cluster on the wheel. not considering possible gear duplication, it's a 15sp. i've put this setup on three of my cruisers, including my favorite at the moment.
if the goal was to end up with as many gears as possible, there's a 5 speed version of the trike hub (or the most i've seen anyway, could be one with more), and i could go with a wheel made to take one of those 11speed clusters (not sure of smooth shifting of the trike hub if the cluster isn't somewhat "fixed" like the shimano cluster is) on a sram dual drive hub, if it would take an 11, might be limited to 9. i could also add a triple ring crankset with a tensioner at the hub.
but like i said before, the most gears wasn't the actual goal. but if i ended up with the parts (like i lucked into an 11speed wheel over the summer) and an idea for probaly a crazy burrito bike, i might try it.