There's space for another platform on the viaduct on the other side of the tracks on the side towards the docks... Just long enough for a 5 carriage train I think
With a bit of joined up thinking it's feasible to have that platform in use just on match days with a separate entrance. That way they can have one for each direction
They could also make the station access northbound only after the match if things get too busy on the island
Although most locals will be going north, a lot will go to Sandhills to go south and then onwards to the Wirral etc
By far the best option is a new station next to where the canal goes past the Titanic hotel. It would be good for the ten streets as well, plus at the new build flats they're planning. The viaduct is wide enough for two platforms. The track will need realigning though.