Cleethorpes to Manchester Piccadilly or Doncaster to London King’s Cross add on? Would be good possibly Grimsby town to Lincoln etc
I agree that TPE and KGX are both needed - but TPE don’t run to KGX so it wouldn’t be the same add on I don’t think.
TransPennine Express don't go to Lincoln or King's Cross so they're ruled out. Cleethorpes/Hull to Manchester Piccadilly the best bet for the 185s, Carlisle to Edinburgh for the 397s, Liverpool to Manchester (Chat Moss) or Newcastle to Edinburgh for the 802s), or Scarborough to Leeds for the 68s+Mark 5 carriages.
802s between York and Newcastle too. Perhaps that’d be another reason to get ECML same era as DON-PBO as a ‘merge’ type thing (if they do DON-NCL)
TPE 802's have run between Doncaster and Peterborough on their way to/from Eastleigh so could layer in from an appropriate route elsewhere.
I think they were there for pre-service rectification and may be going back for attention to the bogies following the cracking issues a year or two back.
But when talking about regular service, it'd be better sticking to the routes they operate on. However, if Eastleigh were to come to the game, it could be a good idea.