Its doable but only with NWNX and still with many restriction. And the NWNX plugins that can do this arent public, virusman afaik never finished it and Sinfar doesnt share their NWNX plugins.
So say you get hands on that plugin. Then you need to apply custsceneghost effect on them so they can be stacked on same place. After that you need to change their Z position with the NWNX plugin.
As for limitations, even creature altered this way cannot pass through obstacles on ground, so even if you had creature flying in 10meters, she wont be able to fly over boulders, water nor raised terrain borders.