I agree, EGSY could be a great little GA field - the Sheffield Aero clubs could move in from Netherthorpe and its tiny runways. It's not really any more congested than Cambridge, which also has its prevailing runway climb out over a built-up area, but doesn't have a restriction on singles.
They might end up losing the ILS, but at least the place would be utilised and bring in money.
There's a strategy for Peel - move the scheduled stuff to Finnginley, get SZD's singles ban removed to be a decent GA field for South Yorkshire, at the same time keeping most GA movements out of Finningley. Maybe this is their strategy?