Well, I guess the easy way around it would be to switch it out for an actual DC element with a much lower resistance, so that you could wire your panels to a much lower voltage and use cheaper/safer switching and protection devices. Depending on how long your wire runs are it may end up more expensive in pounds of copper wire, but for a lower power setup it will probably be cheaper.
Regarding lower power, my limited experience so far is that 1100w out of one element does a pretty ok job on my water heater. So i would add that there's no law saying you need to get the full 3000-4500w that the existing elements are rated at, to have an acceptable hot water experience.
Also, i wouldn't try to convince anyone that a water heater is LESS dangerous than they think, because usually thinking the opposite makes us act more responsibly, but.. If your tank is basically 100% full of liquid which basically do not compress, it is not really storing 'explosive' energy and if it ruptures it will mostly go PUH and dump all its water out. But if you manage to heat the water past normal boiling temp before it ruptures, then AS the tank ruptures the water will undergo phase change and expand by a huge amount, which is what is creating all the 'thrust' of a flying water heater. ? So basically don't heat past boiling EVER, and your explosion potential even if the tank DID fail, should be pretty dang low. A tank rupturing at 180f would be pretty uneventful unless you were standing right next to it in the wrong kind of shoes.