If the new platform 1 is used for the terminators from the south, instead of platform 4, that would remove the conflicts. Whether it will be used that way is another matter.
According to the signalling scheme plan I have seen there will be no connection from the Filton direction to allow northbound trains to directly access the new platform no.1
Health Warning: The plan I have seen is dated 2011 (yes, the new platform has been planned for that long!)I have now seen a more up to date Signalling Scheme Plan and I can confirm there is now a signalled route through the currently
OOU▸ facing crossover at the old Filton station that will allow trains to access Bristol Parkway Platform No.1 directly from the Bristol
TM‡ direction without conflicting with Down Trains using Platform No.2 heading to the South Wales direction.
The new route uses a new chord line converted from the existing Stoke Gifford freight yard shunting neck. This facility also means that there can be parallel departures from Bristol Parkway to South Wales and Bristol TM at the same time. Its actually better than that as there are facilities for three parallel movements at once, either arrivals or departures or a mix of both, Platform No.1 to/from Bristol TM, Platform No.2 to/from Avonmouth and Platform No.3 or 4 to/from South Wales. So all in all a very flexible layout for a change