Yep, granny gearing is the only way to make it possible to move more with the pedals than what you can move walking the bike/hand truck. Mechanical advantage, leverage and such.
Get that chinese trike. They have crazy big brake levers. Like two foot long lever mounted on the down tube, standard issue. "Even better than the Worksmans..." duh
I know you're sold on a trike, but for others reading this thread, Lord Chaos' post rings true based on my experiences with the trailer.