Lots of weapons are in need of balance in terms of something other than cost/upkeep. All of those seldom used/heirloomed things. In the case of the Arming Sword, why not just add some weight to it. Make it resist block stuns more readily for the loss of some length and damage. Or increase the speed a bit. For any given weapon there are really three factors we can alter to make it desirable: weight, speed, and damage (since we can't really change length).
Let's look at the Falchion. 30 cut, 96 speed, 80 length, 1 weight.
Now the Nomad Sabre. 29 cut, 102 Speed, 87 length, 1 weight.
So for about a third less upkeep and 1 more cut damage, I'm losing 8 speed and 7 length by using a Falchion over a Nomad Sabre. God, that is... just awful. Why do we even have weapons like the Falchion in the game if they're just this bad. Any item should be competitive in some way- if you don't want to mess with the speed or damage, jack up the weight. But honestly, make all of the stuff close to the top of any given Shop section more viable instead of throwaway gags. Give them the buffs they deserve.