The new proposals would see the 46-year-old building demolished and replaced with a lightweight roof over a new concourse and public area, with space for either the existing or new shops.
City council bosses have agreed to back the project with a £200,000 contribution towards the next stage, which will see more detailed technical assessments and design work carried out.
The council is working with Network Rail, which owns the station, and public transport executive Nexus – operators of the Metro – which will share the remaining £400,000 bill for the first stage work.