I would like the BR Class 14 to appear at some point in the future, quite a few in real life at Heritage Railways around the UK
And being diesel-hydraulics, they would be a good fit for WSR. However, I personally think that WSR is very well catered for in terms of locomotives, with 08/09/20/31/33/47/52 in most game modes and scenario designer adding 101 (with or without a 31). If they were to expand the number of useable locomotives for WSR I think that the best option would simply be to allow the 08/20*/31/37/66 to haul a rake of normal coaches in scenario planner. Remember that the 40/45/blue 47 will also become available soon, to add even more options. If they were to do this, we would have 11 locomotive classes and the class 101 DMU suitable for use on WSR, which is far more than any other route and more than enough considering that it has a relatively low capacity. *I don't own the Class 20, but assume that like the 31 and 37 it is only able to haul the consists it uses in TVL.
The Diesel Hydraulic WR fleet needs more coverage as only 1 of the 5 classes is represented at present. Would be great to run on GWE as this was their old patch.
A Hymek or a Warship would seem to make more sense in terms of running on GWE as well as WSR due to their much higher speeds.
The complete set would make a great DLC pack and comprises of Classes 14, 22, 35, 41 and 42. Examples of classes 14, 35 and 42 exist in preservation and can be modeled from the real thing, whereas classes 22 and 41 were all scrapped and would be a little trickier. However, class 22 is currently in the early stages of being built from scratch by the Class 22 Society.