Yeah, after the Empire took control they started to find other sources for clone templates and also supplemented their ranks with regular human recruits. They also dispersed the cloning operations, so that there wouldn't be one single source of cloning operations. That way if one facility was destroyed, it wouldn't really have a major effect on troop strength requirements, because they'd have other facilities to supplement their forces. Otherwise, the Rebellion could've just targeted Kamino from the get go, and really did a number on the Empire.
I had always heard the reasons the Commando's had different accents, was because of the different dialects they picked up from their Mandalorian Drill Sergeants. Since most weren't all from one single planet (Mandalore), but from all over, they would have had different inflections. Jango's was supposed to have been a Concord Dawn accent, supposedly.
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