How do you see joining the Army as a way of getting a commercial pilot's licence?
Why would the Army recruit someone who only wished to join as a last resort and who intended to leave for an entirely different career as quickly as possible? Likewise you should not think of the RAF as a means of becoming an airline pilot - your idea just doesn't work the way you imagine it would.
Your three strategies have now been reduced to two, and you need to do a bit of research into the modular and integrated paths.