how to attach items to a unit (wich you have removed the attachments from)
1. make a new item, and give it the desired buffs and abilites, wich you also make
2. make a new trigger
3. make following trigger:
Events:
Unit - A unit aquires an item
Conditions:
Item comparision: Item-type of (Item beeing Manipulated) Equals to <name of the item you just made>
Actions:
Special Effect: Create a special effect attached to the <hand left(normally the weapon slot hand)> of (Unit manipulating item) using <imported weapon>
to make the weapon disappear when the item is dropped just do another trigger saying that when a unit loses an item equal to the item u made, it will remove the last created special effect ^^ (will involve variables if more than 1 unit shall use theese kind of item at the same time, since all cannot be the last created special effect

)
if you want the attachment to be permanent, you can remove the Conditions and replace the Events with Map Initialization