Shouldn't be too complicated, although SKSE might be needed for additional papyrus functions. You would have to make a short "quest" to set up the dialogue and scripts. You might want to look at a papyrus tutorial or two as most of your mod would have to be controlled by scripting.
http://www.creationkit.com/ShowGiftMenu_-_Actor - I haven't actually used this before but you could probably use this to give weapons to the npc after you talk to him.
You could then attach a script to an NPC or a reference alias he is filling in the quest. It would look something like this...
Scriptname _test_testscript extends ReferenceAliasEvent OnItemAdded(Form akBaseItem, int aiItemCount, ObjectReference akItemReference, ObjectReference akSourceContainer) if akSourceContainer == Game.GetPlayer() ;make sure the new item came from the player if akBaseItem as Weapon ;make sure the item recieved was a weapon akItemReference.SetItemHealthPercent(1.6) ;SKSE FUNCTION endIf akSourceContainer.AddItem(akItemReference) ;give the item back to the player endIfendEvent