It wasn't too big back in the day, though it still gets very busy when it's a hot summer Saturday or when they've got gigs on at the Priory.
They've kept it as it's listed.
Forster Square isn't that bad, with the retail park next door. It's about right for what is a suburban train station, could do with some toilets. I'm not sure what you think is lacking about the Interchange? Cafes, toilets, a newsagent, cash machines, pretty much ticks all the boxes you'd need.
Sunderland is a good example of a station that is too small for the city it serves but, again, it is largely a suburban station for Metro. It doesn't even have a toilet, but it does have a very scabby Burger King.
For grandiose stations way out of keeping for the settlement, you can't beat Carstairs (pop 914) but I know fewer expresses stop these days.