I know Bristol only from occasional visits, so would not have noticed that the present outer platforms are wider. I presume the curvature and stepping distance have been made better and that attempting to recreate the layout of the OP's photo would cause them to get worse - a complete no-no from health and safety point of view. I'm sure they would have considered putting in one island rather than reactivating the old Brunel station, so there must be good reasons not to do so. Perhaps the extra circulation space in the big train shed offers more potential for retail development (I remember there is already at least one pub) as traffic grows.
But only one, besides that and the wh-smiths BTM is desperately in need of more retail outlets.
For the first question they are planning an expansion and for the second question there is an underpass now.
Whilst I agree that the main function of a station is travel, Bristol Temple Meads does rather pale in comparison to other comparable stations at "Regional Capitals" on the retail side. Leeds, Manchester Piccadilly, even Birmingham New Street and Sheffield are far more fitting as major stations.
What sort of retail do folk have in mind? The very wide subway has quite a few food outlets already. There used to be a hairdresser down there, next to the gents, in my young days.
Though more outlets on the "unpaid" side of the barriers would be a good money-spinner for MR...
