Thanks for sharing your “system” with your fellow readers. I guess it works very well if everything runs perfectly. Perhaps there would be some risks as it pertains to delays and cancellations, but nothing that can’t be managed.
I do something similar between Arlanda, Heathrow, and Zurich. I typically come across to LHR twice a month, and I need to be in Zurich twice a month. So, I book ARN-LHR on BA with weekend stay, and then I book LHR-ZRH-ARN on LX with less than 24hrs stopover in Zurich in each direction so I can conduct business whilst in the city. This back-to-back system costs me £400 for each ticket, meaning I get two London and two Zurich trips for a total of £800 or £200 per visit. Hard do beat for Club/Business.
One thought; I would assume someone like LX, LH or even AF/KLM would offer very competitive fares from LHR. Rather than taking BA to for example DUS, perhaps moving airlines all-together is an option?