If you want to make BA your career the only smart move is taking the earliest start date on whatever fleet you are offered. I was only offered long haul as at the time they didn’t have enough internal bidders who met the hour and insurance requirements.
Don’t join BA if your sole reason is expecting a very early command would be my view as you are likely to be disappointed, if only because those who are now getting very junior commands will be in those seats for a long time with very little movement. The only reason Gatwick particularly is going so junior is the need to man up and fly the slots acquired from Monafch internally.