Increased ammo while defending a city

[Leon the Batavian]

Pseudo code

declare
unit_type
missile_unit
etc...

If (unit_type = missile_unit and defender = city_defender)

{

then set ammo_amount + ....% ammo_amount

}

end;

What I mean is while defending a city any missile unit should be able to use a nearby stockpile of missiles (arrows + pila etc..) close at hand unlike the attackers.

*I see this picture the elderly, women and children running up and down those stockpiles bringing their hard pressed archers/defenders extra arrows and pila*

Side note:

I know the city towers seem to have an unlimited amount of arrows shooting at its attackers. So maybe its not fair to add more missiles to its defenders.

And in a longer siege the defenders should run out of arrows while the attackers could resupply, but this takes time because it comes from far. And in game sieges are fought without that supply chain. They all seem like short sieges.

This is just an Idea, maybe this is already in effect or being discussed. Or just not doable or unbalanced.