Fredo was too stupid to do most tasks and too weak to be muscle or command respect from the other guys. So it's hard to see a role for him. Now....what he could have done....was maybe manage the family's LEGIT businesses. He was a straight laced person anyway so that would've fit him. He couldn't survive around the Moe Greens, the Hyman Roths and the other killers. But, he could've funneled the dirty cash into clean businesses (construction, truck driving, gas stations, real estate, restaurants, whatever etc.) and stayed out of the violent side. Problem was I don't know if he would've somehow fukked that up too
Either way he should've played his role and accepted things. Al Capone was the youngest of all his brothers. The older brothers worked for him. They were 4-5 years older than Al but, fell in line while he bossed up. There was nothing embarrassing about it as Al Capone had the leadership qualities to run the operation, the same way Mikey had what it took to be Don. Fredo probably felt jealous and embarrassed that his younger brother became the heir so to speak but, all he had to do was devote himself to his brother the same way Tom Hagen did, admit that Mike was better to run the business and maybe catch a couple bodies and he would've found the respect he was looking for. But nah........the jealously/envy was too much i guess. Breh could've also just left New York, moved elsewhere and never returned, changed his name and never conspired against his brother and he could've found his own lane but, he did conspire against his own blood and he got killed for it.