Keep in mind the V-10 is used for things as small as pickups (F-250) to some of the largest dump trucks:
It is really a lot of motor for the Axis/Vegas units; thus there is no problem with hills or anything with them. Even pulling toads they barely even notice them back there (our old F-350 + 5th wheel was heavier than our Axis + car and still didn't have an issue).
As for CCC: The current Axis/Vegas units are built on the E450 frame which means there is an extra 2k lbs available to play with (the earlier ones were built on the E350 frame).
For water/tank usage: Its been our experience that tanks fill up before fresh water runs out--while dry camping, or even camping with only electric hookup its pretty easy to grab a long hose, or a
5 Gallon Water Carrier and refill the fresh water tank. Emptying the waste tanks usually involves unhooking and driving somewhere (unless you can call a honey wagon).