You could always put another line in on the northern side of the station to have a center turn back platform, there appears to be enough track on either side so you could have full speed overlaps in place if so desired, then you would avoid conflicts when terminating services from Barking.
A diveunder at Cricklewood would be very helpful to bring everything round to that mashoosive interchange we're about to have at Old Oak Common. Either on North Pole and onto Clapham Junction, or simply terminating at OOC adjacent to everything else, or as has been raised, via a link at OOC down to Kew.
It would probably be an optimal solution (for passengers) though if all the services where integrated into a single set of platforms at Old Oak Common on the North Pole Site (Including Southern WLL Services) such that...
Services towards Clapham Junction pass from the NNML or WCML (SN) to pass through in an Easterly direction at 6tph, 4tph from Barking Riverside and 2tph from Watford Jcn/Milton Keynes Central.
Services from Willesden Junction can then loop around in either direction to pass through the OOC station in either direction, aiming for Richmond or Clapham Junction, at 6tph, likely to be all to Richmond.