I honestly think the indirect freekick is the only solution unless it's Suarez-style goalkeeping. As you said, getting a goal due to a random bounce in a sport where games regularly end 1-0 is just stupid. It's never going to happen though as Liverpool won Spurs in the CL final after a random bounce and no one said anything.
Being saying for years that the rule is easily fixed.
Did they gain an advantage from the handball? Yes, then its a pen/freekick, removes any argument about intent or natural positions etc