In my opinion wiping the overworld and the voidworld is the best option. This way you don't punish players for moving to the overworld.
When this modpack got created initially, there was no voidworld, so everyone would have to make a base in the overworld anyway. The voidworld got added almost at the end of the modpack getting released.
You can compare this modpack to our other fully overworld based servers, only difference here is that you also have a voidworld.
When resources get depleted and there are no more spots for people to settle, there's a full wipe.
How is wiping the overworld where people built there base fair? You punish the players that want to play the modpack as an overworld pack.
If there is a wipe of both the overworld and voidworld, we should change to overworld to function like the nether/end on the other servers. Having no border (thus eliminating the problem where people die when they use their own overworld portal) and wiping it every month so the resources get replenished. A message where we notify people of the overworld getting wiped should be shown pretty often, so people don't build their base there by accident anyway.
In the end this seems like the best option to me, but feel free to give us your opinion.