This is less a specific suggestion, and more of a complaint about an existing game mechanic that could have a number of solutions, a few I will put here but that do not cover the full range of approaches.
Specifically, terraforming at a large scale is very largely hindered by the fact that player-placed walls prevent enemy spawns. Creating artificial underground deserts or dungeons is impossible without use of external tools, I cannot customise back walls in existing biomes without removing spawning spaces and a misplaced hammer swing can cause irreparable damage to a biome. In a world that evolves as much as the player does, customisation is important to me and I dislike the limitations to building of backgrounds and the suspense of maintaining an existing biome while modifying it.
As previously mentioned, this issue could be balanced a number of ways; two simple methods could be to only restrict spawning in NPC housing (which is still limiting to players attempting to create larger scale non-spawnable spaces) or to tie spawnable spaces to the type of wall (such as those crafted in Ecto Mist), which is again lacking in proper customisability in the case a player wishes to use a nonstandard, unnatural tile in a natural setting. The only solution I could think of (but that seems ham-handed) without limitations to players or repercussions for existing builds is a variety of paint crafted in Ecto Mist, applied via roller, which converts player-placed walls to "natural" walls whether the wall variety could spawn naturally or not.
Specifically, terraforming at a large scale is very largely hindered by the fact that player-placed walls prevent enemy spawns. Creating artificial underground deserts or dungeons is impossible without use of external tools, I cannot customise back walls in existing biomes without removing spawning spaces and a misplaced hammer swing can cause irreparable damage to a biome. In a world that evolves as much as the player does, customisation is important to me and I dislike the limitations to building of backgrounds and the suspense of maintaining an existing biome while modifying it.
As previously mentioned, this issue could be balanced a number of ways; two simple methods could be to only restrict spawning in NPC housing (which is still limiting to players attempting to create larger scale non-spawnable spaces) or to tie spawnable spaces to the type of wall (such as those crafted in Ecto Mist), which is again lacking in proper customisability in the case a player wishes to use a nonstandard, unnatural tile in a natural setting. The only solution I could think of (but that seems ham-handed) without limitations to players or repercussions for existing builds is a variety of paint crafted in Ecto Mist, applied via roller, which converts player-placed walls to "natural" walls whether the wall variety could spawn naturally or not.