The layer can be expanded , chakra redirect could/would not simply leave the weapons in that perfect formation.
Against kidomaro Kaiten was still more way efficient since
blasted away the attacks and the second time kaiten was used it was
halted by chkra stopping
chakra webs halting the expantion/rotation of neji's chakra.
Ntn stops neji from expanding his chakra layer since he already shown he can expand chakra released from the body as a whole.
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U can argue that it would likely take more chakra to expand the chakra layer , but not that its impossible simply because kaiten is more uselful for certain situations.
But if u still agree to disagree its cool.