The only place confusion seems to occur with London Terminals tickets is on the Thameslink route. So I think how that is handled needs to be looked at, particularly as Crossrail will be opening in a couple of years causing similar problems.
On other routes, I don't see the problem.
Unfortunately on some routes it's a very complex problem
Take Tunbridge Wells for instance. According to London Terminals mapping these are the valid stations
<Terminal>BFR</Terminal>
<Terminal>CHX</Terminal>
<Terminal>CST</Terminal>
<Terminal>CTK</Terminal>
<Terminal>LBG</Terminal>
<Terminal>VIC</Terminal>
<Terminal>VXH</Terminal>
<Terminal>WAE</Terminal>
<Terminal>WAT</Terminal>
That's 50% (9 out of 18) of the London Terminals.
From Tunbridge Wells, most customers go to Cannon Street or Charing Cross (or London Bridge or Waterloo East, which are both through stations rather than 'terminals'), as that's where regular direct trains go to (via Sevenoaks, Orpington and Hither Green).
You're entirely valid via Redhill and East Croydon into Victoria though. Or via Orpington and Bromley South into Victoria.* Or via Orpington and Herne Hill into Blackfriars and City Thameslink (but no further north!). Or, when London Bridge is fixed, via London Bridge on Thameslink to Blackfriars and City Thameslink.
And finally, because you are valid into Victoria via Clapham Junction, you are also valid into Waterloo (via Vauxhall, which also counts as a 'terminal').
If fares were simplified, the minimum set of London stations I could see being acceptable to people traveling from Tunbridge Wells would be:
- Charing Cross
- Waterloo East
- Cannon Street
- London Bridge
- Blackfriars
- City Thameslink
Although it's worth noting trains get diverted to Victoria when there's a problem (but that could be managed on an ad hoc basis).
Finally, of the London Terminals that are currently valid from TBW, five of them (Vauxhall, Waterloo East, London Bridge, Blackfriars and City Thameslink) are not actually 'terminals' in the sense that a terminal is defined in the dictionary. No wonder customers are confused.
Maybe the solution is something like this (on a ticket / website), with the restricted group of 'just' six:
London
(BFR, CHX, CST, CTK, LBR, WAE only)
With links and maps available online / via the booking process to explain clearly.
There are probably around 10 such logical groupings that would cover 90% or so of origins. Advance fares can be to a named station, and if there is a flow that's only valid to one station (e.g. Ealing Broadway) it could also just specify it.
The advantage with this approach is that we don't have to start giving names (like "London Terminals" or "London BR" or "London Southern Group") to groups of stations, when people clearly don't understand them.
Anyway, long post over.
*There are many other routes through the spaghetti of south London to Victoria, or indeed to Blackfriars.