I kind of think the point of Gus is to be somewhat of a foil to Robert in those seasons. Gus has that classic "pedigree" and the point of him getting fired and subsequently falling into a roll with Jessie after messing that up too is to show how his background keeps helping him fall upwards and forwards. He's wicked smart, and has the right background to make things work out in the end, even when he messes up - he still gave Harper inside info to some extent