I see what you mean. Sometimes, these akward positions could ''drag'' a job on for longer than you had anticipated or quoted for. Then leaks results, leading to more time being wasted or worse still call backs. aaaarrrrrgggggg.
If such box spanners exists, I am yet to come across one.
You could try some type of filter removing tool or similar? I have one in my van (rarely used), but am struggling to remember the exact name for it? It ic actually made by Rothemberger too.