I want to supply standby power to both units in a separately metered duplex from a single permanently installed generator. The cheapest way to do this is a pair of bog-standard ATSes and a smallish loadcenter to serve as a generator distribution board, vs. having independent generators for each unit.

However, is there a Code-legal way to implement this, given that residential/light-duty ATSes are not available with a switched neutral pole (for instance, you cannot get an Asco 185 with a switched neutral), and that 300.3(B)/310.10(H) likely prohibits parallel neutral paths, such as the one shown in the diagram below? (Hots and grounds are omitted for clarity wherever possible, and so is everything downstream of the ATSes.)

diagram of looped neutral situation with service equipment, generator LC, and two ATSes

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