Unethical? Probably. Illegal? Unlikely. Fraudulent? Almost certainly. Desperate? Definitely.
This sort of question is the distant, poorer, relative of the "is 7 hours enough to enjoy the heathrow lounges" posts. IMO lounges are, with few exceptions, like second-rate hotel lobbies without the option of choice as to what to do next. For the irregular traveller they're surely exciting, albeit heightened by the journey that follows. For the regular traveller they're a welcome respite from the monolithic culture of airports. However neither would willingly pass away time in the Arrivals lounge other than for necessity of washing or watering. I personally hate going to airports without lounge access, but to feel the need to buy a ticket and potentially delay a departure just to visit the BA lounge over the perfectly acceptable No.1 Lounge means some perspective is lacking.
It is a bit like the pair of £650 Ballenciaga Crocs I saw advertised recently (
Ballenciaga Crocs ?!). Sure, some people will do anything to get hold of a pair, but at the end of the day they are still Crocs, and the less exclusive version is less likely to make you look like a plonker.