Sometimes, I swear people do things just because they technically can, with no consideration of whether they should.
While I'll grant you that it would be possible to transport a container of molten aluminum, the idea of doing so is setting off all kinds of alarms in my head. For starters, the insulation and containment would account for at least a quarter (and likely closer to half) of your weight. The energy required to melt an aluminum ingot is a pittance compared to the energy that was required to reduce the bauxite in the first place, so once you're dealing with metallic aluminum, most of the work is already done. The energy you'd save by transporting it in liquid form is more than paid for in dunnage and insurance.
Trucking red-hot ingots wrapped in insulation on flat beds? Sure... I can see doing that all day. But that isn't even close to what it would take to transport it in liquid form.