I wonder if KO1a OLE work will also involve gauge clearance to W12 south of Bedford - unlikely, perhaps, given the intensity of the Thameslink timetable.
Very unlikely. There’s a number of tunnels that would be extraordinarily disruptive to clear (slow lines Belsize tunnel being the worst) Several few bridges on minimum clearance (Victoria Street St Albans being one) and the inconvenient point that gauge clearance of the south MML doesn’t really help many intermodal flows.