There is a Special Ability which can improve that lift capacity by 50%, but that still isn't much (For the mathers, Tonnage/7.5).
An Atlas isn't going to be moving a Behemoth around any quicker than the Behemoth could get their on its own. For those Vehicles which an Atlas CAN carry, it would only help in situations where they are going up/down a LOT of Level Changes, and most Hovercraft of that weight are still better off on their own.
Although, now that I think of it, it would be one way to possibly prevent them from targeting the carried tank. Useful for when that Hovercraft is hit and loses the ability to move, but you want to preserve the crew.