No, I agree - I don't know what the solution is at Central. Those reports only suggest that the problem is recognised and that 'Work is currently underway to understand what interventions may be required' - to alleviate the overcrowding there. They do suggest things like wider platforms and improved escalator provision - but, that's not exactly going to be a longer term solution to the forecast growth in numbers using the station. Also mentions the new trains would have bigger capacity, but as mentioned already, most of that extra capacity will be standing - so not ideal.
I've been rolling this around in my head the past few weeks.
I read up again on the old St James Place station on Wikipedia, and it been updated to mention that a station in Chinatown by the Black-E was also under consideration, and arguably had a better business case. It could well be that such a station follows the new St James Place station towards the end of the current decade.
In terms of the congestion at Central, my only real idea has been reinstating some form of high level station close to where Exchange Street station used to be, and diverting the Kirkby and Ormskirk trains there. Much of the original infrastructure to divert a rail line is still there. There's a building site in the way, but it seems to be one of those ventures that has collapsed as no work seems to have been done for at least 12 months. If push came to shove, then maybe a new line could be diverted around the project.
It wouldn't need to be a big station - maybe four platforms, with some sidings. I realise it would be a pain in the arse for people used to getting off at Central, but it would likely only add about 10 minutes walking to somebody's journey. If they're really that desperate, they could always change at Sandhills.
Central can't be expanded, and there's only so much lipstick you can put on the pig, so to speak. If they're serious about dealing with congestion and managing footfall at peak times, then what needs to be done is divert trains away from the station.