More plot holes
What made the crooks so sure all four people would drink the drugged coffee at the same time? If the drug was fast-acting, it would knock out the first person who drank it before the second person even received his or her drink. Once people started dropping, the remaining people would get up and act rather than sip their coffees.
Were plastic masks the only disguise the crooks could think of? If Joe had dyed his hair or worn a moustache, he'd have had additional protection in case his mask came off.
Where was Joe's backup plan when Mickey stiffed him for his share of the jewelry heist? Joe knew Mickey was counting on him for the "Swiss thing," so he knew Mickey had an extra reason to withhold the payoff and thus retain his leverage. Yet Joe had no plan to retain some leverage of his own.
Where was Joe's backup plan to protect Pinky from harm? The guy had a niece living nearby. As Mickey demonstrated, the niece wasn't hard to find.
Where was Joe's backup plan at the boat? Sure, he hid the gold, but he got shot once and could've been killed several times over. Only Mickey's tendency to rant saved him.
Where was Joe's backup plan in the garage? You could hypothesize that Fran knew or surmised about the black bars, but what about Jimmy Silk? The crooks fooled him once with a fake cache of gold. Was he so dumb he wouldn't check the bars, even though he hadn't seen any proof they were gold underneath the paint?
The only thing preventing Jimmy from shooting Joe was his promise to Fran. Well, what if Jimmy never meant to keep his promise? Did Joe have a backup plan to protect himself from a final bullet?