BA had a Gatwick based British Airways subsidiary called British Airtours which worked very well. They used to swap aircraft and lease crews to mainline BA as seasonality dictated, they even had an almost identical livery and branding making aircraft swaps fairly painless. They even had their own crews and AOC.

The main issue today is the need to offer Club and be "the real" BA when it's not actually BA Mainline doing the flying.