This tool ends up being pretty similar to what you're describing, though the balancer doesnt have holes for the puller (as brilliant an engine design as the Mopar 3.5 is in many ways, the harmonic balancer is an exception).
I've done this job before on this car, and used a serpentine belt wrapped around the crankshaft pulley with vice-grips holding the belt together. I just decided I wanted to duplicate the "right" tool for the job this time instead of killing another belt (before you tell me I should replace the accessory belts, they're nearly new. I replaced the radiator recently, and changed the belts at that time).