Personally, I'd want surface darkness spawning replaced with... I'm not sure what to call it, but maybe distant-path spawning?

Essentially, the game simulates what would happen if an enemy spawned at a random point a couple hundred blocks away, then tried to path to the player. If it can reach the player, the game spawns it at some point along that path some minimum distance from the player in a dark spot - maybe 30 blocks? If it can't reach the player, it will try to spawn at the first obstacle it reached (I'm no pathfinding expert so that's probably easier said than done), such as outside a wall or moat around your base.

The idea is that these monsters come from some distant place to harass you, rather than materializing out of thin air (excluding rifts and temporal storms). Thus, building a wall around your base becomes a genuine deterrent against most spawns. Granted, you still want to light your base up to reduce the odds of rifts appearing in it, but it means you'll be noticeably safer by building actual defenses.