As of right now, the Main lines from Stratford to Shenfield sees nine passenger trains and two or three freights during a standard off-peak hour each way.
To start, I would attempt to squeeze a tenth (and possibly eleventh) off-peak train in, allowing a five-minute headway between trains on this part of the line.
The two freights would be ran as normal, possibly switching to the Electrics at Ilford if Crossrail timings permit. However, for simplicity, I'll assume they stay on the Mains.
-Southend will keep operating at 3tph from London, but to keep speeds, all Romford calls will be removed. Crossrail should be able to take the slack.
-The two single branches (Colchester Town and Braintree) will also keep their hourly service. If Braintree is rebuilt to become a two-platform station, service will be 2tph. Again, Romford calls will be removed.
-Clacton remains as usual. No changes.
- An hourly service from London to Harwich Town will be added, using the tenth path unless the aforementioned Braintree change happens. It'll call Stratford, Shenfield, Chemsford, Witham and all shacks to Harwich after Witham.
The big change will be with the Ipswich and Norwich trains. These three will go all the way to Norwich. Two will be expresses (calling Chelmsford, Colchester, Manningtree, Ipswich, Stowmarket (1tph), Diss and Norwich), and the third will take the Ipswich train's path. An extra stop will also be added at Needham Market to give the station a needed direct train to London.
Someone else can rebuild the WAML...