Neutrals for generator circuits

[Jserra55]

I plan to install a subpanel to feed several circuits.the circuits will be connected to a manual transfer switch fed by a portable generator.the circuits are now in the main house panel,so,can I simply extend the hots to breakers/generator wires in subpanel and leave neutrals in main panel or do I need to have the neutrals originate in the subpanel along with the hots.the neutral in house meter base stays continuous in power outage.

 

[bwat]

Sounds like there may be other things going on here as well, but see 300.3(B) about keeping all circuit conductors together. Would it be in violation of that?