Not to mention a fail-safe MPPT would/should just crowbar the input if there's any potential for overvoltage.

Solar panels are current sources that waste their power into a long string of silicon PIN diodes that eventually reach their forward voltage and begin to eat up all that juicy current. You can just take the current and keep the voltage as low as you want, just make sure to take all the current or it's voltage will rise to let the diodes take the current you aren't using.