Exactly why do think people like Lon Suder and Chell were allowed to suit up?
The Maquis renounced their citizenship in disgust of Federation politicts and some of them might have been patriated by the Cardassians.
Neelix wore a uniform in year of Hell.
Was that because there were no replicators and clothing was at a premium or was neelix doing 90 percent of Tuvoks job after he was blinded?
Did Icheb even wear cadet uniform or was his schooling just a regular education and not Starfleet acasemy courses even though he and Naomi were wearing uniforms 15 years later in Shattered?