The platform allox at Piccadilly have always seemed to involve a circus of the Crewe, Chester and Stoke departures, now including the new de-Southported Alderley Edge (I'm not sure exactly why but it has certainly been that way for a few years now)
At the moment the :46 Stoke sits behind the "new" :38 Alderley Edge on p5 (and sometimes the :30 South Wales makes a cameo!), and the :10 CLC Chester appears to sit behind the :06 Crewe on p8.
I know from experience that the Chester used to sit in front of the Stoke train on p9, even when another platform often seemed free, although in this case the Crewe had p5 to itself!
Inevitably the doors to the rear unit are opened at best immediately after departure of the front train, but are often left right up until (and past) the booked departure.
The real issue I suppose isn't the allocations themselves (which are mainly unavoidable, someone's going to have to double up at some point) but Northern's habit of locking out units - particularly when the staff of the rear train only appear post-departure time!
I can understand why: on the rare occasion that the rear unit is unlocked (and there was a period where they seemed to trial leaving them), someone does inevitably get on the wrong one and end up one or two hours out of the way - but it really doesn't help everyone else!
There must be a better way to signpost front and rear units - if not A/B/C, then something else more than the single cursory announcement and inconsistent display of 'Front train' on the platform screens.