Parkway is a busy interchange, I would not avoid it. However you could certainly do with realigning Westerleigh Junction, possibly Grade-separating it, but certainly straightening it out. Yate Jn would also need to be reconfigured so that the freight connection came off on the down side rather than the up as current. Moving the junction back towards Parkway would also make a 3rd line between Parkway and the junction more viable, which could potentially help with giving regulating opportunities for freight, or to allow trains to London and Gloucester direction to depart simultaneously.I think XC suffers from closure of the Midland line where it now snakes around (using slow flat junctions) between Yate and Bristol via Bristol Parkway (a relatively pointless stop as most services East-West from there can be reached by XC trains at Reading or Newport / Cardiff), the Parkway routing adds quite a few minutes over old route via Mangotsfield, so would be good to see it reopened as a cut off
It would be extremely nice if a single-track east-facing curve could be snuck in as well, to avoid freight having to route via Bath and Dr Day's Jn but that's off-topic.