You actually wouldn't have to have the notch on the kidney plate to do SWAT... SWAT isn't a one for one of the FISD's Centurion. Centurion is taking into account the "whole" of clean white TKs. SWAT is saying, "I'm THIS trooper." Since there were so few of them on ANH we can do that. Therefore if it's not seen on THAT trooper you don't have to have it.
It's why some people have to actually change their armor from 1) getting in the legion (backpack needed for a TD)... to 2) getting deployed (possibly 4 holes cut in the teeth).. to 3) getting SWAT. Every stage is a different level but also, sometimes, backtracking in a way.