And as far as I know "peltastes" was also more or less a synonym for "mercenary" in the 3rd and 2nd century what gives ground to many speculations about gear and fighting.

A question: when were the hypaspistai called peltastai? A hypaspist for me is someone "under/behind the aspis", the elite unit was named after the big shield which they often used instead of the smaller phalangite pelte. I didn't know that this changed later.