Connections to the branch occur only hourly, and with the Ipswich service as an ‘additional’, there is no need for a Manningtree call every 30 minutes.
The same applies to Stowmarket. Three local services every two hours (two-hourly Peterborough and hourly Cambridge) means that only needs an hourly call on the grounds that connections can be made.
Colchester is an odd one. I’d say half-hourly is entirely correct, but at the same time it has an array of suitable services to London and if you were able to extend the Cambridge service round there I’d actually call that a ‘win’. If you make sure the calling patterns of the legacy Great Eastern electric units are a bit better, aka providing an additional ‘fast’ every hour (decelerate the Ipswich and the Colchester Town, massively accelerate the Clacton) and you can probably argue for only an hourly Norwich service, assuming there’s another two an hour to Ipswich (Cambridge and legacy Eastern terminator).
Chelmsford is an obvious one not to bother with. Stratford I’d say now should be half-hourly, not least because of the masses of connections it offers.
So perhaps something from Liverpool Street in the order of:
- XX:00 Stratford, Colchester, Ipswich, Diss, Norwich.
- XX:03 Stratford, Romford, Shenfield, Ingatestone, Chelmsford, Hatfield Peverel, Witham, Kelvedon, Marks Tey, Colchester, Manningtree (now pretty much caught by the Norwich, meaning connection to Harwich but also a connection for Colchester punters onto the Norwich), Ipswich.
- XX:14 Stratford, Shenfield, Chelmsford, Witham, Colchester, stations to Clacton.
- XX:17 Stratford, Shenfield, stations to Southend.
- XX:30 Stratford, Manningtree (connection guaranteed to Harwich), Ipswich, Stowmarket, Diss, Norwich.
- XX:33 Stratford, Romford, Shenfield, Ingatestone, Chelmsford, Hatfield Peverel, Witham, stations to Braintree.
- XX:37 Stratford, Shenfield, stations to Southend.
- XX:44 Stratford, Shenfield, Chelmsford, Witham, Kelvedon, Marks Tey, Colchester, Colchester Town, stations to Walton on the Naze (hopefully then caught by the Clacton after making the smaller stops and therefore a sub-20 minute connection at Walton).
- XX:57 Stratford, Shenfield, stations to Southend.
That allows freight to leave in a healthy gap between, for example, the XX:03 - XX:14, XX:17 - XX:30, and XX:44 - XX:57 eastbound from Stratford, and if you build the timetable backwards into London you get the same result. If you can actually work on a parallel move over platforms 10 and 10a three times an hour the timetable will be very resilient, and there’s lots of regulating / pathing stops available. Ilford eastbound using the slow lines, Shenfield London-bound, Chelmsford eastbound, Witham, Marks Tey London-bound and Colchester. Bar London Gateway traffic almost entirely from the Great Eastern (or have an open 45mph path between Channelsea and Woodgrange Park every hour both ways) and you’re probably sorted.