Wouldn't doing that require you to do some re-wiring on the output side? Since now Y is going to a different pin than usual?
Also, I came across this adapter:https://store.retrofixes.com/collections/kits-parts-accessories/products/av-component-to-scart-passthrough-adapter-audio?variant=33738326474
This is specifically meant for gamers who use a SCART switch into an RGB monitor that accepts both RGB and component. This adapter will allow for example a Wii plugged into the SCART switch and when it's being used, you simply need to hit the toggle switch on your PVM/BVM to go between RGB and component (and ext/int sync). IMPORTANT - It will not work in any other scenario and if you are using a gscartsw, it will only work in port 1.
It looks like it passes component through the Scart pins like you are looking for. I want to use this too when I get my gscartsw for my Gamecube.
I have a PVM that can switch between Y-Pb-Pr and RGB with or without external sync.
I'm assuming it passes Y through pin 9 and 11, which would mean that the gscartsw would not detect the sync.
I don't know why it says that it only works on Input 1 though (is something special about input 1? I thought only 8 was "special" in that it was the default passthrough if no sync signals are detected), furthermore it looks like it wouldn't fit in input 1 but only intput 8 because the rca stereo connectors would block port 2.
The problem with that connector is that, as you said, it uses Y signal through green in RGB. In other words, it uses pins 9 and 11 instead of 17 and 20. And also, $25 for a piece of wires like that seems to be quite expensive for me.
I guess "input 1" is "input 8". Just think about it. It depends on how you start counting ports. Whether you think the nearest to output is the last one or the first one.
Regarding to the extra wiring, that's a good question. Could that be solved with configuration at OSSC? Could a firmware update for OSSC fix that? That would be interesting. Another option would be that Superg included a manual selection of inputs in future iterations of the Gscartsw.
Once I know what's the way to follow, I'll order some RCA and SCART mounts and I'll design both the PCB and the 3D-printable case.