I wouldn't recommend it as a permanent attachment. You can do that, and in 0.3a you'll have several options of accomplishing it, but be very careful. Attaching a modeled object to someone will cause crashes in scripted chronicles and in some cases non-scripted chronicles doing 'jump' sequences.
Do not under any circumstances allow players with model attachments to be 'jumped' to a new location. They can walk through exits all they want, but an automated jump on the side of the chronicle or by the storyteller interface can cause crashes if players are having 'modeled attachments' to them. This is a game engine problem and cannot be corrected by Java scripting.
NOTE: The reason I know this is because in E-Mod 1.8's early stages I had did wearable helmets, which don't have any problems in single player, but crashes in multiplayer when I was testing Leaves of Three. I later found out it was the combination of wearing a helmet and being 'jumped' at the same time that caused the crash.