Hardwired also protects against EMP and CUAV jamming. Including if you are in a car. Putting car protection on Stealth will make the perk too powerful considering all the other things it does.
In any case, I could probably make up a bunch of preset classes made up of options not normally available in custom classes. Since they are preset you cannot change them. Will depend on whether or not it will cause any major script problems of existing stuff but I dont think so. It's already set up for multiple tier choices via Gambler.
edit: Recharging should be 30 seconds but the hud element is likely showing miliseconds. Flak Jacket will protect you against cars unless it explodes at your feet. EMP Countermeasures should kill a car completely even if the player has Hardwired. Unless I missed something and will check. For balance, nades are obviously less powerful than the mine. The flak jacket should reduce explosive damage to %40 of normal assuming the enemy doesnt have sonic boom. However since this is hardcore, with only 30 health, it will still kill if close.