When you pick up the item it could ask you in chat if you would like to attach suppressed, armor piercing, ect in chat
eg:
You have picked up a (weapon name) The following available attachments are listed,
1. Suppressed, 2. Armor Piercing, 3. Rapid Fire ect...
Then just say /1, /2, or /3 to attach it to the weapon. You could also put in a function where if your holding a weapon, you can say, /attachments to open up the same options...
This might not be possible, but i think its a good idea at least.