My next suggestion is for Southeastern High Speed and the pack could include... Class 70 (Diesel-Electric) in Freightliner or Colas livery (useful for other modern routes). Class 377 in Southeastern livery. Class 465 variants in Southeastern livery. Class 466 in Southeastern livery.
If I'm 100 percent honest if DTG were to release this it would need to be free. The route already has all of the rolling stock which you would usually see and different variants of trains we have would be cheeky if we had to pay for them
Each type mentioned requires its own work and would therefore cost money and in turn require paying for.
The only EMU's I really want to see are those that step back a couple of generations - VEP's and CEP's in the case of Kent. Problem with any non HS1 traction for SEHS is that you only have a fairly short section of route to run them on.