They're pretty solid ideas, but you also have to think:
Mechanics that wield wrenches to fix money printers:
Money printers only overheat/explode. They never "break". It would probably take a lot of extra coding to add in malfunctions.
PC Mod computers do lag the server, and they're rarely used anyways. Most people set them up, and forget about them. I personally think they're pointless.
Merc. starts with lockpick/keypad cracker:
Mercenaries already start with a gun, that means that's one less thing they have to worry about buying. If they started with a lockpick and keypad cracker, they'd be self sufficient and the economy in-game would topple.
Mechanic can sell cars:
If you don't like it, why even bring it up?
Soldier class:
That probably will be in the future, but it'll probably end up being smoke, not flash, because both can be used as a minge tool, but flash debilitates a player, smoke only annoys a player.