Actually, on the topic of mandatory stealth play, there is one such area in the Sundowner level. It's the floor where you destroy the three generators hidden in the walls. If you want to collect all of the left arms for Doktor, you have to take out everyone on the floor without being detected. That condition met, a hammer guy with a collectible arm will spawn in the large office.
That whole sequence is a pain if you're impatient like I am, but since it's the only section of its kind, it's not the worst thing in the world. I had more trouble landing an accurate slash to sever the arm than I did avoiding detection.