Take another look, every Mirage seat that I have seen has 3 connectors. 1 for the seatbelt buckle(idiot light), 1 for the side airbag and 1 for the seat position sensor that's on the front rh edge of the seat track. If the airbag or seat position sensor is unplugged you'll get an airbag light. I'm not sure about the seatbelt one. I think someone had trouble trying to bypass it. Or maybe either the 18's eliminated the seat position sensor or it's not used in the US?
I posted wiring diagrams for a 2017 Mirage a while back. They are gonna be more relevant than the go-to 2015 service manual from the sketchy Russian site.
Are you fabbing up your own mount brackets or use some self tappers and call it good?
View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)