Mobs that spawn by default with held items default to holding those items. I.e. skeletons will spawn with bows, and setting helditem to sword will not override this.

Maybe make it so that you can do "helditem" : false or similar wording to remove the default helditem, which then could be followed up by "helditem" : "desireditem"

edit: on further looking at the code, it looks like skeletons spawn with a bow if you allow the regular spawn event to occur, regardless of how the code is called.

Looking at how summon works however, spawnspecial can be used to keep a mob from spawning with items.

I'm not sure if this would only need to be done to skeletons, but would it be possible for you to implement this in a way to where skeletons could be spawned without bows?

I would also like the capability to remove some of the default items that mobs spawn with. More specifically I would like to remove armor/weapons from all mobs.