"Get a bigger jaw" doesn't seem feasible, and would probably not be very appealing (for aesthetic reasons) anyway. "Get a smaller tongue" isn't much better. It does seem like there might be some kind of retainer that could work. The fact that there isn't already someone making billions from that idea suggests that no alternative has been found that's both effective and convenient. Anything that could keep the tongue from sliding back is also likely to trigger a gag reflex. Or maybe there is a solution in that area, but nobody has quite hit it yet.