The idea of turning a dead run into a service is fine in theory but there is a whole host of problems before you even start.

Dead runs 'do' have a reccomended route you take but in reality you can go whichever way you want (there are some exclusions with drivers being told to avoid Newcastle with non compliant vehicles on dead runs).
Driving time may be an issue if there is a delay on a dead run service and a driver can't divert off route.

Breakdowns, especially first thing on a morning before a bus leaves the depot or on route to the starting point. Deptford has been short on morning PVR a couple of times because of this (you either wait for a repair, a different vehicle already in the garage to be repaired or a bus back from scholars workings).

I for example, run light from Deptford to Coxhoe. There are a dozen different ways and variations I can go with some quicker than others. Limiting this to a specific route could impact on the service the vehicle is due to run onto.