The problem is if they stay you'll probably finish up with a small fleet of 333s and a small fleet of something else, instead of a decent size fleet of one class of EMU, which reduces maintenance costs and costs related to crew training and clearance.
We already have a small fleet (16) of 333s and a small fleet (8) of 321/322s in Yorkshire.
Without knowing the numbers of additional units required in Yorkshire, I would say the first thing to do is move the 5 Heathrow Connect 360s to Greater Anglia and then 5 321s to Northern, so as to keep to types already in use. Further units than that are probably tied up with the main TP North fleet order in my view.
Theres also the question of where how the franchise map is divided up. If East Coast becomes a multipurpose franchise, and if the Northern/TPE franchise is devolved to the PTEs (looks like West Yorks, South Yorks, Merseyside and TfGM) there may be pressure for the Newcastle TPE services to not be part of the devolved franchise. In this case they could go to CrossCountry, which coupled with the Manchester-Bournemouth and Manchester-Scotland services could make a sensible hub for electric XC services from Manchester.
That of course changes the stock required, perhaps Manchester Airport-York could be operated by 'local/commuter' stock and Liverpool-Newcastle by 'intercity' stock?