The current 07/25 runway could probably sustain ATR 42/72 operations, albeit with weight limitations, especially with a wet runway. If something larger is envisaged the problem is probably not extending the runway length but extending the declared distances to something nearer the current 1834 metres runway length.
The current restricted landing distances could be of more significance that the take-off runs available.The problem appears to be roads passing through the undershoot to both runways which then result in significant reductions.
The roads themselves are not the cause of this, its the 4.8 metres above the road level (to allow for a high sided vehicles) that requires the insetting of the thresholds.
Traffic control is a possibility, but as jumping the lights appears to be a national sport in the UK, CAA may not accept this a resolution.
If the road situation is resolved, the current runway with a 30 metre width could result in a take-off run/landing distance of up to 1799 metres. If anything greater is required, the runway will need returning to its original width, 45 metres?
Next problem would be re-locating the approach lighting, which may be outside the aerodrome boundary. Is this feasible?
What is the intended market for the airport, PAX and/or freight? If freight is intended presumably much larger aircraft will be required which will require the runway widening and extending plus the taxiway/apron infrastructure to support them. Hope Stobart have deep pockets if this is intended.