The thought of a Slig's possessed pants make me laugh!!! Can you imagine it... these pants moving by themselves and the Slig not knowing what's going on!!!
As for security orbs it would make sense that Munch could possess them... but there would need to be some way to surpress Munch from chanting in some areas too... so they might either have them effect both characters... or have a different kind of surpressor for Munch (such as if there is an area where Munch will be able to possess, but Abe can't, etc).
Abe Babe...