We had an RN QFI at Leeming EFTS in 79 who'd been FW carrier qualified as a Mid, but he might not have been front line.
I joined as an 18 yo Mid in 78, and even then I'm fairly sure it was impossible to get to a front line sqn in under 2 years, although I think it might have been possible to do it in ~ 2.25 if you joined BRNC in September.