Seemingly there are at least two proposals under consideration for siting the junction - one roughly where the marker is on the map below and the other further south (closer to Frodsham).
My initial thoughts on seeing these proposals are that this junction seems to be very close to Junction 12 - and on a stretch of motorway that is prone to lorries backing up as they climb the hill when heading east. Also, as we know, this stretch of the motorway is vulnerable to blinding sunlight in the morning in the autumn and spring. Too many junctions in close proximity can impede rather than assist traffic flowing. However having traffic flowing freely onto the Mersey Gateway bridge does make a lot of sense.
Given that we are missing a junction 13 would this be an opportunity to renumber the junctions - so we don't have to use an 'a' - or are we all too superstitious for that?