Perhaps wider use of the Blackpool North system of not letting anyone on to a platform until a set (and generally rather limited) time before departure might work.
Aberdeen operates a variation of that system. Seats are provided on the southbound platforms and passengers can pass through the barriers and head towards them when a Platform is advertised but, as soon as they attempt to sit down, they are accosted by a staff member who demands that they return to the concourse (where there are not enough seats) because "the train is not ready". After milling around on the concourse for a while, the passengers are called forward only to find their tickets are now rejected due to "passback". The staff then open the gates to let them through .... the pièce de résistance is that at no time is an Advance ticket checked to ascertain which train it is for.
Surely such a superb system warrants a wider roll out !