The other physical options to speed up radiometric decay involve messing with fundamental constants in ways that make every atom fall apart (making the electromagnetic force weaker), make protons and neutrons fall apart (making the strong nuclear force weaker), or make all neutrons turn into protons (making the weak nuclear force stronger). Incidentally, the first one would also require slowing down the speed of light, thus making ancient starlight even more of a problem.
The only options left are a (pointless and deceptive) miracle or invoking magic.