I've given this thought for quite some time. As I see it there are a few distinct schemes:
Leeds to York
Piggy backing on presumed TP electrification of Church Fenton to Neville Hill, add Micklefield to Selby, Hambleton East-North, Hambleton West-South and Gascoign Wood-Church Fenton.
Allows for a collection services (with a small amount of change reversion to historic service patters) to go to electric operation, giving a good uplift in electric service numbers, and providing electrified diversionary routes to a number of routes.
Sheffield to Leeds and Doncaster
Create a new electric triangle by completing South Kirkby Junction to Swinton, Swinton to Doncaster and Swinton to Sheffield (via Masborough and Rotherham Central).
Allows Leeds to Sheffield via Moorthorpe, Sheffield to Doncaster, Sheffield to Adwick to go over to electric operation, plus potentially bimode operation for CrossCountry extended from Haymarket to Sheffield.
Clearly Leeds to Huddersfield is now specifically on the agenda (and doesn't have any obvious small add ons), but the above schemes I think would make most use of the existing wiring while also maximising the service miles converted to electric operation.