Agree with THS.
I have huge respect for the training that JTs do, and having done 2 flying sqn tours, I am glad I don't have to change an engine at 0330 in Norway. A JT demonstrates self management, maturity, patience, reliability, diligence and thoroughness. A L/Cpl demonstrates the ability to organise to an unhealthy degree, to keep discipline, to motivate (by the boot if need be), to know when to crack the whip and when to offer an ear, and to get scared, tired and hungry men to do unnatural things.
Perhaps the rank would have long term benefits. Making the larger than normal transition from Tom to full blown NCO is something that is needlessly difficult (its the biggest promotion leap) for the least experienced servicmen. Given the deployed nature of their roles, I wonder why TSW, TCW, MCSU etc don't also have the rank, although I hope the RAF doesn't decide to use it across the board as a cost cutting measure by stifling the promotion flow to Cpl. Although of course, where the Regt leads, the RAF does tend to follow.
(Forget - You probably still need that badge in Woodston or Dogsthorpe don't you?)