The Gallagher family in Shameless is absolutely flawed, but they of course do have a lot of love for each other. Conflict has been a common theme between them all since the very beginning, but they often have been able to find ways to push through it. Thus, this has been able to make them a very fun family to follow, as it certainly has been able to provide a lot of realism. This is even the case still with the show being in its final season.
However, there were a lot of previous characters who could have been intriguing fits in the family. In some cases, they were previous partners who should have been around more, while others may have just been smaller characters who provided a lot of humor when around. The show certainly integrated Kev and V as a part of the family, but other characters could have been excellent as long-term members too. It could have provided a lot of intriguing storylines if the showrunners decided to go down this avenue a bit more.
The friendship between Mikey and Frank was so strong. It was a shame that it was short-lived though, as Mikey purposely went back to prison to receive free medical care. Mikey needed to be a bigger part of the family.
Although Mikey was flawed, it would have been cool if he engaged with the other Gallaghers more. It was clear that he meant a lot to Frank and it would have been hilarious if he partook in crazy hijinks in their house.
Mandy was the one who got away with Lip. It was hard seeing her leave the series, as she clearly cared about Lip more than anyone else. This was evidenced by her doing everything for him, even if it was not appreciated in the slightest.
Although Lip ended up having a baby with Tami, it could have been nice if they decided to make Mandy a bigger part of the Gallagher family. This did not come into fruition, but it certainly was warranted given how much Mandy loved Lip.
Jimmy was a part of the family during the beginning seasons of the show, but it quickly ended. This was disappointing, as his connection with Fiona was simply the strongest out of any of the other men she dated.
Given the fact that he also dedicated a lot of time to them, it was strange that his story took such a dark turn. However, his criminal activity made it inevitable. Had he opted to avoid that life and stuck to medical school, perhaps he and Fiona never would have broken up.