My thoughts on the Andor TIE Avenger having so many more weapon hardpoints than the X-Wing game series version (and most other Star Wars fighter types) is that the one Cassian steals is an experimental testbed.
They just stuck everything on there to see which system would work best, and the production version would probably have either the wingtip mounted lasers OR the gatling ones; either the torpedo launcher OR the missile rails. Maybe those extra two seats in the back were for observers during test flights, or engineers to make sure the ship didn't melt itself.














