Neutral/grounding for a manual transfer switch handling 2 generators

[FAZERS]

I want to design/install a transfer switch circuit for 2 off-grid, 15kW (208Y, 5con) trailered generators that will travel from site to site together on the same trailer. This is just for a means of redundant power -- not parallel power -- so ideally no output synchronization is necessary as the two will never be concurrently connected, nor do I want it to be physically possible for them to achieve this connection. I have been looking at manual transfer switches (MTS, henceforth) and mostly find up to 4 pole switching units. This, combined with NEC 250.30's guidance on Grounding Separately Derived Alternating-Current Systems, makes it apparent that I'm most likely going to be switching the 3 phases and neutral, while providing a system bonding jumper from Gen1-->MTS, and from Gen2-->MTS, per my interpretation of 250.30(A)(1) System Bonding Jumper code.

I want to be sure that I'm interpreting this correctly while minding the anecdotal "only a single grounded source," so my main concerns are:

1.) Given that only one generator can transfer electrical power to the main circuit at a time, is this still OK?
2.) Do I need to provide an additional, direct bond between Gen1 and Gen2?
3.) I would of course like to be able to start the un-switched/"offline" genset for a few minutes first to ensure it is mechanically sound before manually switching over. Is there any code to pay attention to regarding this? (I don't think this would cause any fault/imbalance issues with any onboard electronics, but am not confident because this application is a bit unusual.)

Thanks

 

[W@ttson]

maybe this helps:
https://www.trystar.com/article/con...y-derived-or-non-separately-derived-system-2/

 

[FAZERS]

Thanks.

It would appear in this example, the multiple separately-derived sources achieve compliant grounding via non-direct grounding conductors (daisy-chained through the transfer switch chassis) and that this didn't require a dedicated grounding conductor directly between Source 1 (Service) and Source 2 (Genset).