Some suggested I did the same when I wished to surprise my parents at the airport and take them into the lounge, it is as people point not only completely unethical, it is illegal as fraudulent and may well result in loss of your status loss of any unused Avios, cancellation of future Avios based travel or indeed a ban on future travel with BA.

Certainly not worth it and I paid for a quick RFs trip to PRG in order that I could guest my folks in, which they absolutely loved.