Personally from an impartial point of view (as i'm 100% not a farmer) I would like it to be impossible to rein a grey players, it just encourages troll players to gain some kind of recognition. I see no skill in this and it leads to a less challenging servers, as players either quit & start another server because of spiking or they stop farming and have weaker armies. spiking affects all players not just big/elite players, it also takes away from the little guys too (who cannot rebuild their troops as easily & usually end up deleting)
all players should be allowed to farm (or not farm) grey players at their leisure, maybe it could be added into quests to make it clear to new players they are allowed to steal resources from grey villa
just remove resource production of grey villages until they get active again. Way easier to solve, maybe increase resources from robber hideouts or lower defence.