Hi there Nigel,
Yeah you are right, that is a lot of power, and bad for the eyes if not anything else.
I could imagine a 500 watt white LED from 2 feet away. It would hurt the eyes very badly.
Conclusion: not a good idea to take the door off
This reminds me of an episode of South Park where one of the main characters, Randy, wanted to be able to buy medicinal marijuana but the doctor said nothing was wrong with him so he could not get a referral. Well, the next day we see Randy holding his mid section up near a microwave oven with the door open and it running full blast in an attempt to get testicular cancer so he could get a referral and then buy 'weed'. It was funny as heck, especially when his lower man parts both grew as big as basketballs, and he had to bounce around on them to get anywhere in town.
The writers of that show are truly the textbook examples of crazy (ha ha).
As I've mentioned previously, an old friend (now sadly long since deceased) worked on radar during WW2, and he had two RF burns on one of his arms (I can't remember which one) from adjusting them. Apparently who had to reach deep inside the transmitter to adjust something, and every time you did you suffered two RF burns, about an inch or so across, separated by another inch. He told me that everyone who did that job had the burns.
And of course Microwave Ovens were developed (and the idea came from) that work during WW2.