Elite Africans

[Strategy]

Hannibal's army was in Rome, operating in enemy territory, with the only friends being Celts and Rebellious Italian communities. It stands to reason that Hannibal's army ended up looking like Gauls/Romans/Italians. They were supplied with clothes by a friendly Gallic chief while crossing the alps. They looted arms and equipment from the fallen Roman dead (of which there would have been a lot of equipment, fairly early on in the war). Hannibal's army was made up of mercenaries; one should not expect that they were equipped with the very best of equipment. It stands to reason that they would jump to the chance of getting a nice good chainmail shirt or fine Italian cuirrass (an ornate Oscan triple-disc cuirrass was found in Africa - probably war booty) if they got the chance. Shields wore out quickly - the Italian Scutum would be the obvious replacement (they are not likely to have shipped in new ones from Carthage). The same goes for helmets; Roman and Italian helmets are the obvious replacements for the helmets worn out by long service.

It must have been extremely common that armies finished campaigns looking very, very different from when they started. Caesar mentions how Pompey's troops had become very "hispanic" in their fighting style. His own troops no doubt looked more like Celts than proper Romans (having campaigned for so many years in Gaul).

There is no reason to suppose that Hannibal's troops adopted Roman gear because the equipment of the Roman legionaries was uniformly somehow "superior" to their own. The troops looted the dead, and took use of the rich gear that they found - such as the expensive chain mails (keep in mind that many - if not most - of the Romans would have been using pretty poor gear; their armor would have been a simple bronze pectorale). Roman armies were not uniformly equipped. The African infantry, having a proper breastplate of Linen would probably have considered themselves equally well protected as a Roman infantryman with a pectorale (though obviously - not compared to one with a chain mail shirt).