IMHO it's only a shame if there any possibility of putting back into use makeing something. The Panther factory had no future and at least the supermarket will create a few jobs until probably the next recession when the supermarket market will be swamped.
When I was part of the automotive industry I had Albion in Glasgow as a customer. At one stage (1950's) they made a whole truck from bar and billet in a series of sheds along the Clyde plus engines, gearboxes and so on for other people (Enfield included). The modern axle production and stores use one bay out of eight and the workforce is down to a couple of hundred. To be honest they'd have a more secure future if they moved to an industrial unit in Paisley and sold the old factory for flats. Investors don't like Victorian sheds with leaking rooves and huge derelict spaces, they like industrial units with white painted floors and lots of visible activity.
I think eventually they might build a supermarket on the Harley factory. They've already turned the original into a museum I believe and at some point the existing factory will be either too small, in the wrong country (unlikely) or too big.
I hope they put something up to mark the Panther site though. They can at least call it Panther Road or something.
Andy