Maybe when the full line to Seoul Station opens it will be a suitable alternative.

Having the locals run much more frequently than the express sort of defeats the purpose of the express trains. The time you save by taking the express is lost to the time you spend waiting around for it to depart. Having flipped through the A'REX website, it looks like the express trains have different seating arrangements and suitable luggage-storage areas, somewhat like the Airport Express in Hong Kong. That could be a reason to take the express, but an hour between trains is really ridiculous.