It's very unrealistic and will never happen, but I'd argue the Gloucester area needs 2 new stations. One, as you've suggested north of the city to serve the areas such as Barnwood, Longlevens, Insworth and Churchdown etc, but there also needs to be one south of the city, to serve the rapidly growing areas of Quedgeley, Kingsway and Hunt's Grove. If either were to be a parkway, I'd say the south of the city station would be the better option, as it could be better located to the motorway and the roads driving into the city centre from Quedgeley and Kingsway are often a lot more traffic-heavy than the roads from the northern areas, it could potentially encourage more people out of their cars and onto public transport that way? It would also serve as a better interchange for those changing between the bristol line and the golden valley line. Keep the current station for the services through to Newport and Cardiff, but stop most of the services (maybe not all, keep some peak trains perhaps?) that have to reverse at Gloucester.
Realistically though, nothing will ever happen towards even considering the thought of additional stations, because to put it nicely, the council here are absolutely useless (unless somehow the Bristol Metro plans can somehow push for them and create business cases?)