Consider making creature & item spawn points as area based instead of specific coords? I'm sure we'll still want to have the option of making spawns specifically located. Area based randomized spawning within a painted sector would be more dynamic/engaging.

As far as sector properties, my plan is to change the map format.
I want to make "sectors" layers that you paint, instead of having any specific boundaries.
Sector data will then just be part of the one-time map import.
Same with monster spawn data.

This'll be quite the project, because, for manageability, I'm going to have to make a library for map reading/writing shared between client and server.

Although, if you're going to be working on a new map editor, then being able to set (and view) sector properties through the map editor would be prefered.