Ambush. You put them on hold-fire, hide them somewhere and then toss a grenade and decloak when an enemy squad wanders too near. Like Commandos.
Like current live Stormtroopers with Stgs you mean. Expect the live version has other uses too.
Live stormtroopers have the following problem:
1. Unupgraded, they are just buffed, more expensive Grens with the exact same weapons.
2. Their upgrade is too costly.
3. A unit with bolt action rifles and nade-on-cooldown is useless for infiltration purposes.
4. Way too expensive for what they do.
5. Beyond the near useless infiltration spawn, they will operate as regular infantry most of the game with an occasional ambush. At which point they are again either Grens without an MG42 or very expensive buffed PzGrens without a true unique role.
The solution to this is:
1. Slightly different mixed weapons profile, found to be work well with Volks
2. Slightly cheaper upgrade at 75. Solved if they can spawn with a Stgs.
3. Already solved if they spawn with a Stgs. Not more than two, because that would be Op for infiltration.
4. Solved, since now they provide an intermediate weapons profile between Grens and PzGrens, with upgrade to be semi ShrekPzGrens or PzGrens with ambush.
5. With their versatile armament and upgrades, they can be anything. A versatile infantry unit that can fill the holes in OST infantry line.