I would not disagree with the principle but it's unlikely to be a barge as they have tried that a few years back and it ran into all sorts of problems which is why they switched to a small feeder vessel for the service to Port Salford further up the Ship Canal. However, that has not run for a couple of years now and in recent months the Canal has been closed beyond Warrington for maintenance which if navigation is to be maintained eventually reflects in the costs which in turn limits the capacity of any vessel deployed on the route. At best that capaccity is currently limited to about 350/400 teu and at best you might just get three round trips out of a single vessel subject to tidal and weather conditions and the locking in and out at Liverpool and Eastham. The problem is what you do with the feeder if it's not sailing up or down the canal as all the feeders operating out of Liverpool nowadays are 868 teu and above, so it's difficult to see how such a service would be a viable proposition.
My point about the need for upgrading the Seaforth railhead was more to do with the fact that any direct service from Asia and/or the Indian Subcontinent would generate a huge number of containers, many of which would have previously been routed via Felixstowe, London Gateway Port and perhaps Southampton. So whilst the B&M facility would generate large numbers on it's own, there are facilties in the region such as the huge TJ Morris and Amazon etc warehouses at St Helens on the border with Warrington with will generate substantial numbers in their own right. Ten years on since Liverpool 2 opened, the terminal has largely managed to steadlity grow volumes using mainly road transport for it's distribution mainly across it's natural catchment areas across the North of England, Midlands and North Wales. However, to service the wider UK market, it will become necessary to increase the volumes moving by rail simply because the road transport industry will not necessarily be able to sustain long term growth. .