I'd just discovered this 'fixed' nature of the camera input and yes indeed it makes sense (except they should have fixed it to PAL). Don't you feel better gwc now that you know
ika do you also know about the (composite) AV input to the Tuner module? Is that fixed or variable with the TV setting? Seems to me it would have to be fixed as if you have something like a DVD connected, that will stay the same wherever you travel, just like the camera. But to fix it to either format wouldn't make sense as any equipment you buy to connect to it would be in the default format for that country, e.g. PAL here in the UK and therefore not necessarily the same as that to which the input is fixed. What logic did BMW use on that little conundrum?
I just saw your diagram of the 2 relay setup. Not sure I completely understand why it is necessary though. Maybe that's becasue I don't know the schematic for the relays. Do you have that, what terminals are for the coil and which ones are switched?