I've been shopping around for trikes since my initial post and I've come to realize that indirect steering works best with a single handed operation. And most manufacturers with indirect steering systems offer a one-handed kit you can either install on the left or right end of the handlebar.
The one-handed kit usually includes a gripshift for the rear derailleur, bar end shifter for the front one and a single brake lever than activates the brakes on both front wheels.
I think that's what I'm aiming for.