I didn't have a problem taking out the plugs in 2.0's or SOHC/DOHC 2.5's without jacking anything up. You're all a bunch of pussies.
Unbolt and swing the washer tank and intake tube out of the way, depending on how much room you want/need. Get your socket and a short 3/8 extension onto the plug first. Then drop the ratchet down there and snap onto the extension and break the plug free. You'll be able to detach the ratchet from the extension and spin the plug out by hand with your finger on the extension. Repeat for all four. Installation is reverse of removal. I prefer to put a very small dab of high temp antiseize on the threads before installation. Spin plug until it seats, with your fingers first. Then torque to proper angle as specified by plug manufacturer. While you've got the coils off, it might be a good idea to inspect the plug boot for corrosion and wirebrush it + apply a light dab of dielectric grease if necessary.
I've tried using a flex extension before but that just twists enough to piss you off and not go anywhere. After working on midengine cars for years, subarus are a laughable piece of cake.