I am still of the belief that the network is sitll in absolutely dire need of a short wheelbase,low axle load/ RA,go anywhere "mixed traffic" type engine.
Now that DRS are canning a lot of 37's,as they have done with the CL20's, there is still perhaps a niche to fill.I doubt many freight operators are willing to stump up £4m a time for new loco's.
Back to back,or TaT de-rated + re geared HST's with conventional drawgear could perform those tasks previously assigned to the 20's/37's,with much more modern engines and much better fuel efficiency