I have done some work implementing auto input switching on the OSSC. Currently I have added these settings:
Autodetect input -> Off, Current input, All inputs.
Auto AV(1-3) Y/Gs -> RGsB, YPbPr
When there is no sync it switches input very quickly every 0.2 seconds and there are 6 different inputs if you consider RGsB/YPbPr the same input so it cycles through all inputs every 1.2 seconds. With the Auto AV* Y/Gs settings you can select if it switches to RGsB or YPbPr for AV1-3 separately.
When set to Current input it stays on the same physical input so for example it switches between AV1 RGBS, AV1 RGsB only.
I think this should take care of all the various auto switching needs.