It won't be longitudinal. This is one of those things that come up that I can't take seriously. Even if devolved TfL wouldn't do it as they havn't on the Elizabeth line. They have on LO as most lines max out at 5-car and are packed. SE is 8-12 car.
It'll be like the 707s or 376s. More standing space but still enough "standard" seats if that's your choice. Hopefully in formations that can make use of the 8 or 12-car platforms (with SDO unlike the Networkers) which would be good enough for the next 40 years. Not to do so would be stupid. Class 376 s and 707s don't maximise capacity as it is maxing out at 10-car. To continue that with new stock is dumb short-termism.
It'll be like the 707s or 376s. More standing space but still enough "standard" seats if that's your choice. Hopefully in formations that can make use of the 8 or 12-car platforms (with SDO unlike the Networkers) which would be good enough for the next 40 years. Not to do so would be stupid. Class 376 s and 707s don't maximise capacity as it is maxing out at 10-car. To continue that with new stock is dumb short-termism.