One post earlier on the weight of a Vanquish 2M indicates that the total weight is pretty much within the 5115g limit. So the plane is AMA Nats-legal up to Advanced. To shave the extra 115g, one can use lighter CF prop, spinner, and small-capacity receiver battery etc. The extra cost to do so would not be that high.

The FAI weight rule is to restrict people from using powerful and fancy engines, which could increase the cost of entering the game for everybody. I doubt the removal of it will be considered.