Bathurst yard is quite big and there is likely a location with a spare siding that is able to be reclaimed and installed a security fence with security cameras similar to that at Armidale and Canberra.

Electrify to Bathurst then?  

Without the Bathurst bullet going through to central you aint got a bathurst bullet.  

People who think an electric train that will run similar stopping pattern from Lithgow are dilusional.  The southern Highlands has been there done that.  Southern Highlands had a better run time in the time of steam.  Dont think it wouldn't happen to the Bathurst Bullet service and become next to obsolete.  You will have people driving to lithgow rather than catch Bathurst Bullet.  It happens now with people driving to Macarthur/Campbelltown from southern Highlands.

Who said anything about freezing your balls off at Lithgow Station waiting for the connecting service? the EMU should be there waiting at Lithgow when the DMU arrives, and once all have transfered (should only take a minute), it's 'doors closing, please stand clear' and off to the city.

The Southern Highlands change is completely different, it's not cross platform, there is waiting for the connecting service, and the connection is a suburban train with suburban stopping patterns and suburban crowding.

You say the connecting EMU at Lithgow "should" be there, but that's by no means certain. In any event, it's irrelevant because the through Bullet express service in peak hours is going to be far more attractive than being forced to change to what is likely to be a slower journey on the EMU stopping at more stations through the Blue Mountains. I can't see the logic of running a separate EMU "express".

The same principle applies on the Southern Highlands Line. I'll wager that an upgraded and more frequent through service from the Southern Highlands to Central would increase patronage significantly.

Perhaps if it was heavily advertised that changing at Lithgow meant a quicker trip between Bathurst/Orange and Sydney, and more frequent services, it could work.
The logic of running a separate EMU express would be to run more services to Bathurst/Orange without needing more rolling stock.

A through services would definitely attract more passengers on the Southern Highlands Line, the forced change there is a serious issue since it is not a simple cross platform change and does involve freezing on a platform in winter, but the worst issue that the connection to the city is a suburban train with a suburban stopping pattern complete with overcrowding.
Southern Highlands stopping patterns needs to be; Goulburn, all to Moss Vale, all to Macarhur, Campbelltwon, Glendfield, Sydenham, Central

Could electrification to Moss Vale or Goulburn be justifiable? I doubt it could be justifiable to Bathurst or Orange though.