In my replays I just line the front door with LAMs so as soon as the goons enter they blow up. Then it's a massive shooting gallery all the way down. You can also use your leg augmentations to jump down the elevator shaft, and sneak your way to the front door.

The issue with this is that the game doesn't really communicate this fact to you, and not killing the goons technically should mean that they're still going to go upstairs at some point and kill Paul.

The most hilarious part of this is that Paul himself says he's too weak to climb through the window, but as soon as those goons bust in through the front door, he whips out a 50 lb flame thrower and starts strafing around at 30 mph like he's in the motherfucking murder olympics.