The water requirement is shown on the top of the mission, as is how much is presently selected / en route.
If you want an ARR that only selects vehicles based on water, perhaps you should use the "Gallons of water" option? Would that be a workaround?
At present, we are looking at two-sides (both very valid), one side which has wants an exclusive water tanker only, so it increases the gallons of water on scene, while the other side can use the foam tenders to satisfy the Water Tanker requirement on a mission.
I do like the idea & I will give it a go
The only problem I see before I even change my ARR’s to use gal of water is that it will dispatch my wildfire aircraft