I understand that, but if my Powered Armor isn't allowed to be any more effective than Heavy Body Armor, unless the characters can't even get their hands on that, then there's really no point for me to play a PA driver. And keep in mind, Heavy Body Armor, the Item, is the sort of setup used by SWAT officers and some tactical teams in the military. It should be plenty commonplace.
As for the weight issue, that's actually covered by a Defect, the Awkward Size Defect. Yes, I know, it relates to size, but the table for the Awkward Size values also lists weights for the sizes. Table 7-2. An object with no ranks Awkward Size has a weight of 50-150 kg.