Relay contactor switch in IP enclosure fitted under panels a bit like the solar edge units. Presuming the switch and enclosure provides adequate protection against water and fire (and debris) and the contacts inside cannot make again, the only way to get a circuit again would be to join 2 ends of the same half back together. Given the way that most sytems are wired, in a loop there is now a decent distance in between the + and - and one of the ends is concealed in the enclosure.
If required you could have multiple units so that the system is automatically segregated to lower voltage further in the event of AC power being lost.
Can't see a fireman climbing up on to a roof in the dark and rain whilst the house is ablaze with a pair of knipex snipping the cables, which are also concealed under the panels. The unit would effectively do it all by turning the AC off.
No idea how much it would cost, but if it's a real issue then who cares?
Not saying it's 100% fool proof, but then nothing is especially in the health and safety type enviroment.
Just an idea, havent got the time or money to investigate but can't see why it wouldn't work?
