The last thing that is needed is 3 stations what with HS2.
Leeds like much of the north is full of tiny trains. Make them longer before spending £bn on building huge new stations on prime development land.
Start at 8 cars not 6.
If your current platforms can take two or three little trains and you wish to extend then to a point where they reach need their own platform (unless there's platforms which can take 16+ coaches) then there's going to be a need for more platform space.
By building HS2 platforms and removing the LNER services you effectively gain 1 while new platform for local services.
If these local services are 6 (20m) coach services you can still fit two into a platform at a time.
Now given they are local services they can have shorter turn around times, meaning 3 an hour rather than two, so that's 6 services which benefit.
However those services had been taking up platform space elsewhere which can now be used by other services to make them longer. Which then doubles the number of services which can be 6 coaches long to 12 services.
That's 12 services an hour which could be 6 coaches long by the removal of just two long distance trains. In reality is likely to be a bit lower, but even 9 trains at 6 coaches long would be a significant improvement, especially if those services are currently 2/3 coaches long.
Once NPR happens and removes more of the longer distance regional services to the HS2 platforms then there's more scope for more longer services.
Whilst I agree that short services should be lengthened rather than more short services provided, there's advantages to there being at least 2tph from most stations.