Thanks for all the good feedback!
Did this today.
The above is technically true, you can't stealth for long. However, you can stealth to about 5000 points.
Equip silenced pistol. Shoot Commander with headshot for 1300. Headshot enemy below, 2/3 enemies in next room and on deck AND the dog for 4500-5000 points. Make sure health is at 100 still, and you have a lot of assault rifle ammo, then head for the stairs past where you killed the dog.
You should see two boxes. Break them down, then kill enemies with your assault rifle from here. For some reason, this seems to spawn more enemies than if you just go stealth, or if you just go all out. Take some out from the grate and the gap to the left for a bit, then descend down and stick to the rooms on the left. They are good points to take cover, and they don't spam grenades here.
Take out ALL enemies before the commander, and headshot the commander. You will need about 20,000 points before undoing the gate, i had about 22000 from this method. After doing this, its a simple case of trying to get headshots and combos for the remaining enemies.
Always aim for the head, combos, and stay in cover. Time isn't a real factor here.