It takes 3 years to train a GP, but only 15 months to train a pilot
That just shows how little you know about a pilot's job. It is possible to complete a basic training course in less than 2 years if you are lucky and get a job / multi crew course immediately after starting at flying college.
Following that, it takes up to 6 months to complete a type rating and line training before being unleashed as a junior F/O. Starting pay is in the region of £20,000 to £30,000.
At this point you only have a Commercial Licence (CPL) and are not licenced to fly in command of airliners. That takes at least 1500 hours of experience which could take 2 - 3 years. Even then, no airline is likely to get insurance for a 1500 hour pilot to be in command but even if they did that's 4 - 6 years from start of training.
In BA, you need to have 2000 hours experience on medium jets before being elligible for command plus at least one year in the company. Those are flying hours, not duty hours and so will probably take 3 - 4 years to acquire.
So even if the seniority system allowed it, a new cadet would have to wait at least 5 years after basic training before getting a short haul command and probably nearer 10 years.
Do you still think you can train a pilot in 15 months?