Make it so that if you go to an enemie's island you can break their gens by right clicking the signs(maybe for a cost?),but you can't break your own team's generator. This will make it so next time the generator is fixed it becomes less efficient(more time to spawn the same resources). Mid gens can't be manually broken(but the next part of the post does allow for mid gens to break). Edit:If the team on that island is dead you can't manually break that generator.
Editv2: Sabotage Resistance
When you right click the sign you have to hold it down for x amount if seconds depending on generator level.(level 1 easiest, level 4 hardest)
Also maybe it could be so the opposit ehappens to prevent early game generator shutdowns(level 4 easist, level 1 hardest)
Iron can be broken back to level 1 if it was higher than that, it can't be disabled.
Something extra: Generators have a limited life span of how many resources they can produce(3x or 4x the amount of material they were suppose to use ex:a level 1 diamond gen guves either 12 or 15 diamonds before breaking), and leveling them up resets the life span. Once a generator gets naturally broken you can fix it using the previous material: iron->gold->diamond. The price to fix the generator scales by a prices of 8(8,16,24 and so on or a scale of 4 if this is too much). When you fix the generator either 1.The level remains of what it was before breaking or 2. The level resets back to level 1.
Once a gen has broken x amounts of times your team can willingly break it which will reset the cost(and you start back at level 1), but the gen will be less efficient than it was before.(more time to spawn the same amount of resources)
This will discourage camping since if you stay at one spot for so long eventually the fix price will overwhelm. This will encourage taking out other islands to get their gens, and games might become semi-nomadic.