First of all, thanks for taking time and wrote such a descriptive to the point post. I was able to sketch the resistor and capacitor. Please correct me if the sketch attached i drew after reading your post is right/wrong?.
That is really logical.
Each Solenoid (24VDC 260mAmp) is connected to its own IRF540, so 40 solenoid having 40 IRF540. Why do you think the 100Volt IRF540 is not a good choice.
I have no scope i am not electronics engineer... can you calculate the capacitor/resistor value?