I don't think that will work Trevor, the monitor identification appears to be done digitally
https://en.m.wikipedia.org/wiki/Display_Data_Channel
I've tried disconnecting pin 12 and/or 15 but I couldn't fool it.
Anyway, if like me, you are using your normal computer, having a second monitor as an extended desktop is a massive enhancement for normal computer stuff.
Another thing worth mentioning, is there is a useful +5v supply on pin 9 but my cheap VGA switch box does not pass it through, so I soldered a wire link.