I had a quick look at the schematic linked to by the last site ( http://wunderkis.de/vsl-dual/vsl-dual-rev0.sch.pdf
) but I can't see the STM32 in the PDF
However looking at the USB connections they seem to use PC13 and PB2 to get the USB bus to re-enumerate.
I'm not sure why they have 2 pins driving USB+DP, but whatever the reason, you'd need to either seriously modify your Maple mini or you'd need to modify the firmware.
Personally I think the better option is to change the firmware, as the Maple mini has its own USB reset hardware which uses 2 x NPN transistors.
But you'd need to work out why 2 pins are uses as the Maple mini only uses 1 pin to reset the USB.