Baltimore could be a "big city" if the county and city were to formally merge and create some more cohesive urban form between the two. I think you could do this by focusing more growth/development on the former arterial corridors like York Road, Edmondson Ave, Harford Road. I mean, you're looking at over 1.4 million people who live within the city limits AND within the County's Urban/rural demarcation line. If that's not a "big city" I don't what is. I can't think of another place in the Western world where that wouldn't be considered such.