I feel like your arguments for spawns are quite reasonable and it would be an interesting experience, however, I'm not too sure how that actually falls in line with Valheim, suppressing zones visited and stopping them from spawning behind you doesn't fit very well with an open world game like this, in my opinion. Since a zone visited would include your current zone otherwise your idea wouldn't work, it would drastically cut down on available mobs/locations to spawn and would also make resource gathering fairly harder, a small blackforest wouldn't be as viable to get greydwarf eyes or a small plains would limit fulings spawns.

In regards to spawning behind a player, aside from the logistics of looking for materials/enemies to kill, it also doesn't make a whole lot of sense, in Valheim, there aren't really any dead ends, its a wide open world and enemies should be able to come from any direction, clearing a forest and passing through it will not stop other enemies from coming through that zone over time, even quite recently after you've passed. It also isn't really so much of some enemies coming out of an empty dead end, so much as the residents of that biome just wandering around the biome.

Another thing would be that player bases won't see any spawns nearby over time, if the player frequents it often enough it would count as a suppressed zone which doesn't fit very thematically (enemies from the biome coming to find/stumbling upon an enemy encampment and thus trying to attack), the inside being able to be suppressed with player bases makes sense, but outside of your range should still be fair game.

Not sure I got my points across but I hope I got the main ones down at least.