Lol thats exactly why i made the TUUB. It was a 54" deck with no flex that weighed ~2.6kg using the magical power of tubularity. Not very crash resistant though, being hollow and whatnot. The carrying advantage for that deck was more about being able to shoulder hoist it rather than just the weight, tbh
The deck between your feet does create torsional stiffness though, which is another important reason for a tubular deck. If you try to cut out the middle of a plank deck, or even just make a thinner deck with CF skin, you lose that stability. The amount of bias cloth needed to make it back mostly negates the weight savings in wood.
It could shave about 40% off of things like hangers (compared to aluminum) if replicated one to one, but any place with concentrated stress like a bolt mount would need to get beefed up a bit.