It was not uncommon to move from the ground to the air. A lot of Flight Engineers were ex Ground crew. However this option is not open now unless you can get a job on the BofB memorial flight.
Several of the Nimrod Wet and Dry ops were ex ground pounders as well.
I know of an ex Cosford Flight systems Apprentice who went on to become the station master at Waddington and became an Air Commodore at HQ Air. He was a Nav or WSO depending on when you srved. He did have the advantage of winning the Phillip Sassoon Flying award whilst at Cosford as one of the best apprentices. We both come from the same town and both are fathers worked at the same place. No more to say but some of you reading this will know of whom I speak. I do have an interesting story about the person concerned but may save that for another day. He is safely retired now and living in his home county.
So yes, it can be done, but the opportunities are less now than what they used to be.