And I love what they've done at Westminster with the platform doors to stop people topping themselves off the platforms, a very good idea which I think should be introduced all over the country if you ask me. Safety is absolutely vital on our railways as I'm sure most of you will agree.
They've got them at all the deep level stations on the Jubilee line extension, but haven't fitted them on the platforms on either the old (ex Bakerloo) sections or any of the surface stations on the line (including the extension).
The jubilee line has a single stock type, operating always as seven car formations.
For the mainline? Unless you've got a very expensive, complex solution, you have to be able to deal, at most stations, with two or more of the following:
20m stock with 1/3 2/3 doors
20m stock with 1/4 3/4 doors
23m stock with the above
23m stock with doors near the ends
23m stock with doors actually at the ends
20m stock with doors actually at the ends.
You also need platform door SDO (various lengths of trains), additional doors to line up with crew doors etc.
Perhaps on some commuter stations where there really is only one stock calling (c2c for example) it could be workable.
You would also need to ensure that trains always stopped exactly on the mark- not always easy (eg ice, leaf fall season)