If you completely change the npc characteristics using setshape2 to nonblocking, it becomes unclickable and pretty hard to change or delete.
NPC Code:
if (created) setshape2 3,3,{0,0,0,0,0,0,0,0,0};
It also seems like type 20 still doesn't have a throw-through attribute (blocks player, but allowing npcs and projectiles through).
NPC Code:
if (created) setshape2 3,3,{20,20,20,20,20,20,20,20,20};