If you have two routes to one station then you just label it on the front of the train. There are countless examples of where this happens on the network already. How many different routes are there from Edinburgh to Glasgow? People who live on the intermediate stations seem to manage okay.
Going back to the root of the argument, there is a case for Stratford to have an half hourly service to Birmingham all day. A town that size and that proximity to Birmingham should have really, especially when it's a tourist attraction in its own right too. Extending the North Warwicks would be great, but it would give a 20/40 minute service rather than a more evenly spaced half hourly service. Extending a Dorridge terminator would give a half hourly service. Passengers from Stratford could also get to the south via Lapworth or Dorridge (it would require five miles or so of doubling back, but again this happens quite a lot elsewhere on the network)
Perhaps try reading my post in the context of the post I quoted, which was suggesting some extra trains via Dorridge and some via the North Warks line, ie a muddle - which train is via which route at which time? If you have glanced at the timetable, saw there's a train at xx.30 and turn up, then discover isn't not the one going the way you want, you're not going to be a happy passenger, whatever the front of the train says - which people often don't read anyway. Not everyone out there has an intimate knowledge of the way railways work and, as I said, regular intervals rule around Birmingham, so if you must go via Dorridge then make a regular interval that way and a regular interval via Henley but not a muddle at odd intervals one way, then the other. Clear enough?
I hope a half-hourly service works, but it is going to require a pretty drastic growth in custom to wash its face financially, whichever route it uses. Some more fast trains would probably help, but the only obvious way to path those is via Henley and Shirley.
And precious few of the tourists come from the north. Having to walk between Moor Street and New Street is a pretty powerful disincentive, same applies to changing trains at Dorridge. Direct trains and minimum complications are what tourists look for, that's why BR introduced the London-Oxford-Stratford trains to follow the tourist trail, and why FGW (and perhaps other) GW franchise bidders want them back.
Don't be fooled into thinking that a vast amount of new capacity was released down there either, it in effect only added one new signal block between Whitlocks and Henley at Wood End and extended the current 6 minute headway from Tyseley to Whitlocks End instead of Shirley where the AB used to start.
Never suggested it did add a vast amount of capacity, but it didn't need to, as:
a. there is the extra block section
b. All the sections are now available for use when the line is open, whereas in the past Henley-in-Arden signalbox was switched out at times, so the section ran between Bearley junction and Shirley, which meant there was unused capacity previously, never mind now.
And if I was Freightliner I wouldn't be happy about my trains being stuck in loops all day if a dmu using the line could go another way, nor would I expect them to sit there just muttering in their beer about it.
