|The point is not in being able to swing such a blade, it's more having to carry it without bonking everyone upside the head, containing such a behemoth blade indoors, convincing people you aren't compensating for something, etc.|
Also, it can't possibly be made entirely of steel - it's gotta be mostly iron, so maybe it's easier to sunder too.
So a bit like owning a horse. The GM could say 'put it somewhere, hope no one steals it; and if you're really scared, hire someone to watch over it for you'.
And because it's a freaking full blade, it should only be one of the goliath's weapons - his other one could be like a shortsword or dagger (the usual rule).