question

Interesting no one has run across this! Was hoping it would have already been done. 4 AC sources, 2 Quattro's (in any configuration) for the most flexibility.

If not on this forum are there other areas to check?

I'd encourage you to discuss your proposed setup and wiring with an experienced and reputable marine systems electrician -preferably one well-versed in the Victron ecosystem- to determine the best path forward after a full review of not only your existing wiring but also the operation of the Quattro-IIs.
Part of my concern is that the Quattro-IIs each have 2 AC inputs, yes, but when paralleling them you don't then get 4 inputs, you still only have 2, because they're now operating as a single larger unit.

Also important to note that in parallel "stack" mode (for 6kVA output) they won't provide split-phase 120/240 when inverting, but if they're in parallel-split mode where inverted split-phase output would be possible (one unit providing 3kVA on L1, the second unit providing 3kVA on L2) then the L2 input of both units are disabled entirely which doesn't seem like your desired functionality.

I don't doubt that there's a way to achieve your desired functionality, but I do believe it's far beyond the purview of this public forum to determine that, thus my strong recommendation that you consult a reputable professional in the field to work out a plan.

Thanks and the reason I'm on this forum is that I have been working with two different Victron dealers and neither has a solution for this. What is throwing everyone is the use of any combo of 4 AC in's.

1) I do understand, that in Parallel mode, I'll only have 2 AC in's with my two Quattro's. Bummer given the potential functionality that could be enabled in software.

2) It isn't mandatory to have 240v as I can spin up on of the gensets for the occasional dryer run or main A/C.

3) There must be many applications with 3 or 4 AC in choices but I'm not seeing any schematics.

At this point I'm going with a transfer switch between each genset (to AC In #1) and a 4-combo selector switch (2 gensets and two Shore power)(to AC In#2). Not ideal!

***If the software could run two systems with unified control integration and data aggregation, my situation, and many others, could be solved. Two inverters, run through an integrated UI, but with separate power outputs to segregated panels.