Where do you get this info on MerseyTravels thinking?
Saying the Edghill is too peripheral is like saying the Euston is to perhip[erhal, on the many occasions I have been to London, only once have I walked to my destination from Euston.
Edgehill with the fight set of connections would be fine. If you going to the business area the getting off at Edgehill and then using a service via the Edgehill Spur to Moorfields.
450 meter trains are at the moment the minimum that can do the channel tunnel, getting a GC connection to Edge Hill via Warrington Low Level, Ditton and gauge expansion through Allerton to a full GC station at Edghill then with the Edge Hill spur and use of Wapping and Waterloo in addition to most services stopping on the way to Lime Street, would provide enough access from Edghill, superior quicker access for most of the city and still be cheaper than upgrading Lime Street.
It would also, of course, provided a massive economic boost for Edgehill.
I do have some sort of working relationship with Merseytravel (or at least did till recently). That said, I'm pretty sure it's out in the public domain somewhere. Will have to have a look for it.
To address your response: comparing Edge Hill to Euston is apples & oranges. They're both fruit/stations but that's where what they've in common ends. London's a much larger city with a much larger downtown area. In fact, it's multipolar, with more than one CBD: i.e. the City, Canary Wharf etc. The scale means that no matter what part of Central London a railway station may be in, a large proportion of passengers will want to be in another area. Due to the scale of the city, this will often mean using another means of transport (buses, tube, taxis etc). Ideally, Euston would be a bit further in but no one station location is going to adequately cover Central London. Lime Street is actually the better comparison to Euston and not only because they're corresponding termini on the existing London-Liverpool route. Like Euston, some people lament that Lime Street is a bit on the peripheral side and it'd be a bit nicer if it was a little further in. Indeed, Central is much better for shopping, Moorfields is much better for the CBD and James Street is much better for the waterfront. The difference with London is the scale. Much of Liverpool city centre is walkable from Lime Street, although the waterfront and some of the extremities can be a bit of a treck. If anything, Old Oak Common HS2 station is a better comparison for Edge Hill than Euston. It's in the inner city, not massively far from the centre but far enough to not be considered part of the centre. We have similar debates about whether HS2 should stop at Old Oak Common rather than Euston and it's often debunked for similar reasons.
Edge Hill makes sense if your starting point is fitting a 400m station somewhere in Liverpool. Once you start taking other considerations into account, such as convenience for passengers, it doesn't seem nearly as much of a no brainer.
--- old post above --- --- new post below ---
Its only logical and practical that ultimately Lime Street is the terminus not Edge Hill which would be a temporary terminus while Lime Street was rebuilt. From what ive heard they aren't thinking about a southern extension of the station building but making a couple of the existing southern platforms dedicated GC gauge (they would have a slight curve) and moving the track junction further back in to the cutting. The cutting would need some widening. The remaining platforms would only be operating other long distance/inter regional services and Lime Street upper level would essentially have no short distance/commuter services.
Main issue for Lime Street would be embarking and disembarking though. You need more access points the length of the platform than just a single end or you will get severe platform crowding and bunching. That means some kind of mezzanine structure above the platforms.
That is what Merseytravel are looking at, although with the option that if Liverpool is to ever get 400m platforms then they'll be at Lime Street immediately south of the existing sheds. One would hope they'd be captive platforms in the existing station but they were pretty vague on that from memory. Like I said, if it happens, I doubt we'll ever see the 400m platforms or at least not in our lifetimes. They'd switch to double-deck captive trains before going to the trouble of building 400m platforms to take longer single-deck ones.