While Nightmare is indeed a very big map compared to most Solo Eggwars maps, I don't think it should be removed or changed in any of the ways you mentioned. Sometimes players might just want to play on a larger solo map and Nightmare is pretty much the only map for that, apart from the original Construction, which got removed many years ago. This map is truly one of a kind and if you remove it, there won't be as much diversity in the maps and the gameplay as there currently is. Also, removing an individual map isn't gonna solve your problem with campers and hiding spots, as the campers can just play other maps and there are hiding spots on every single map.
Though, one thing I'd like to get changed is the design of the houses on every island, as there is currently only one way to get in and out, and because of this it is far too easy to get trapped inside, so perhaps they can open the window and/or add a back door to avoid that.
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