Would Aramaki able to handle Snakeman like Kizaru??
Kizaru is just a better physical fighter to deal with such brawler from what we've seen. What Aramaki has shown until now is just spamming his giant tree form and his branches, it would be pretty useless vs legit top tier with top class fighting ability.
Kizaru would clapped Morley with bare minimum requirements which Aramaki couldn't............
G4 with all adv haki alone would be a problem for GB who at the moment hasn't shown any feats to quickly dispose him unlike Kizaru.
Being both Admiral doesn't mean one can do what the others could.
GB also wouldn't have the mobility and speed of Kizaru who could dip back and forth while trying to do a mission of killing Vegapunk and defending himself from Luffy.
GB would needed to brawl with G5 allowing Luffy to have actual 1v1 fight.
Kizaru is far more tricky opponent and would be hardest to tagged among any Admirals, but G5 could tag it and was able to land solid punch even when Kizaru was playing a defensive game.
GB who have no choice but to just manfight G5 could end very bad for him.
He'll get far more beat up with multiple advCoC rocking his ass, if he's not Kaido he'll get beaten right on the spot and he's not Kaido.