I'm surprised they don't make the shifters smaller diameter than the threaded part, so the threads are the largest diameter (and with no shoulder at the change in diameter). I guess you'd have to have a larger inside diameter shift knob though, to make the shifter large enough to not break. You wouldn't want a pencil sized shifter just to be smaller than the root thread diameter.
This is the strongest way to do it though, like good aftermarket engine studs/bolts, or just make the shifter and knob from one (expensive) piece of billet. Fuck, my brain won't shut off today.