This is a Modding Resource, meaning any modders can use this in their own mod and modify it to their heart's content, so long as they provide credit to this as the original mod.
Supply Wagon
The supply wagon is a slow moving chariot unit with next to no combat strength. You can only have one per army.
Supply Barrel
The supply barrel is a stationary barrel that is available to defenders in a siege battle. It functions similarly to a bastion onager, in that it can only be placed in specific parts of the walls.
Refill Ammunition
This special ability refills 3 ammunition for all units within a 75m vicinity of the wagon or barrel. For the first 25 seconds, this ability reduces the movement speed of units within its range by 75%. At the end of these 25 seconds, the units regain 3 ammunition, and there is a 50 second recharge on the ability. It can only be used ten times.
Compatibility
Screenshots
This mod is not compatible with Rise of Mordor or any mods that change special_ability_to_invalid_usage_flags_tables.
This units are not available in a campaign, since I don't know how campaign stuff works. Feel free to make them available in the campaign for your own mod.
Download Links
If you download from Google Drive, move the mod to C:\Program Files (x86)\Steam\steamapps\common\Total War Attila\data then launch Attila, tick the mod on and you're good to go.
If you download from Steam, then just launch Attila, tick the mod on and you're good to go.
Thanks to Enpremi and Taro for the idea.