FoSBR» has done some work in this area. We have listed local stations in the West of England and made suggestions on improving access. You can see details of this here:
https://fosbr.org.uk/campaigns/better-stations/Following an event earlier this year where FoSBR drew attention to poorly signed bus/rail interchanges, we have met with
WECA» and may be making progress with improvements to signage at bus stops
https://fosbr.org.uk/interchange-between-buses-and-trains/As they currently stand, Parson St and Bedminster are both difficult places to install access ramps because of the width and length of the platforms. However if Network Rail's aspiration to reinstate four tracks from Temple Meads to Parson St were to go ahead (see here:
https://fosbr.org.uk/weca-strategic-rail-investment-plan/) then both stations could potentially be remodelled. That could lead to access improvements, which might mean ramps or lifts. Given the current economic and political climate, there probably isn't much prospect of this happening soon.