Would this actually be a safe option? If a condom was worn then there would be no actual physical contact. A perspex screen could be put in place so you could see who was actually doing the business.
Or am I taking this all a bit too seriously?
Can never take it to seriously in the current climate
I see what your thinking problem is another 10 blokes may have been in the room before you and done the business up against the screen. So not at all safe.
A better option is if a WG lives in a house with a letter box and in a quiet ish street. Is to arrange with the lady that you put your cock through the letter box and she sucks you off that way. Also possible to invite her to your house if you live alone or have understanding family and have a suitable letterbox(one with soft brizzles is best)
If you have a cat and a cat flap in your front or backdoor that is also an option.