It occurs to me that I could put 12 foot boards over top of the existing decking and have a seamless deck with the boards running in the short direction (perpendicular to the house). I'd leave gaps between the boards for drainage. I could even remove some (1/2, 1/3) of the old boards to improve drainage if necessary.
The deck will be a bit higher but it is already a step down from the house so that won't be a problem.
Is this done? Are their hidden problems waiting to bite me if I install new 5/4 x 6 boards on top of and perpendicular to old ones?