I agree, this would be a great addition. In the meantime, here is what I do to get close: select the fixture you want for POV. Press CTRL-F to set the camera focus to that fixture. Then use "ORBIT" to move the camera around keeping the fixture as the focal point- giving you a camera perspective "through" the fixture. Since I have "free-flight navigation" set to Yes in settings, that means holding down the SHIFT key to put the camera in ORBIT mode. Not quite the same thing as fixture POV, but great for checking obstructions.