Corosive, hello. Do we know you? Are you a developer really? Why have you been so quiet?
Anyway, yes, i always thought Water Merchants in Hub should play some part in a job or quest. Wasteland would be dry so moving water around would make a good job.
The Job
So you use water bags or bottles. You get the job from someone in the Water Merchants area of Hub (which is otherwise not used). They send you on your way and it's always random where you have to go but it's always to a known public location, mostly other towns. You have to fill up as many water containers as you can carry before you go. Recipients give you a receipt (use the note item image, same one from the Industrial Park message quest). You get paid on return when you hand over the receipt, based on distance and volume of water transported. Good job for a group.
Options
If you get a firetruck, whoah-baby look out. You can move a ton of water with that thing so you could maybe make a lot of caps. Or sign up to guard the Water Merchants' own water caravan, which would run in similar fashion to the regular caravans.
Bonus
Also, along the way to deliver the water, they also want you to stop at some farms and repair some broken wells or water pumps. These farm locations could be unique, single-instance quest locations generated just for this job. You get there and you need someone with decent Repair skill to get the extra xp, but often find trouble; random hostile critters to fight (ants, rats, mantii, raiders, deathclaws, etc).