I think the answer is to work out how to protect the wires alone.
Transfer case skids are really intended to prevent damage to the alloy case from contact with rocks. Using a skid plate in the conditions you describe is always going to result in debris collecting on top of the plate. I built a skid for a Sierra many years ago but we have never fitted it because mostly, we drive in muddy conditions so it will suffer from the same problem you are describing.
I don't have much experience with the electric shift Jimny case, but I assume it looks like this (without the breather)
If so, I can see how those wires will be a problem. Firstly, they are only wires - they can be lengthened or moved to make them less vulnerable to damage. Also, a small cover from 3mm steel or equivalent could be made to cover the areas the wiring connects to the case. Even if these areas became packed with grass, it couldn't cause a fire.
I will say though that I doubt there is enough heat in the exhaust piping to start a fire. Catalytic converters can definitely get hot enough to ignite grass (this has been a problem in Australia) but not the pipe where it runs past the transfer.
Steve.