I've always thought that carapace armour is the equivalent of SWAT or some similar "breach and clear" team, and while you might always have access to carapace you shouldn't have that leap up from "naked defence" to "absolute turtle".
If the other armours are available, you could have "patrol", "riot" and "raid" weapons and equipment.
Juves have access to "patrol" level weapons and equipment (flak, stub gun, knife etc), representing that they may only be trusted with that level of equipment and level of activity, standard enforcers and dog handlers have access to "riot" (mesh, shield, shock maul etc) and "patrol", gunners and leaders have access to all levels (raid being carapace armour, and other stuff).
Getting access granted at various levels may either encourage or discourage different loadouts, but it also means that you're not getting bogged down fitting your handful of guys out with super expensive equipment from the get-go.