It's not just ATO which will make things quicker. The (wide!) doors on these new trains can move at an incredible speed, so much so that they have had to be slowed down artificially for one or two reasons, but all in all will help dwell time. Then there are weight savings - basically, fittings have been minimised, hence the lack of plug sockets, tables etc. These will assist with acceleration.
With regards to the door to First Class, there has to be a gap around it to allow emergency smoke extraction to work. The hinge should automatically close it - slowly. It can be locked shut, too, as can two hidden gangway doors, to divide the train up in case of vandalism/if it requires urgent cleaning.
I personally find the Standard Class seating much more comfortable than that in First Class, and to be honest, it feels OK with another person sat next to you. The maximum possible spacing has been required from Siemens, without conflicting with the wheelchair-accessible gangway widths. Legroom is not too brilliant in the "airline-style" areas, but this should be mitigated by the provision of seats with naturally better legroom at the wheelchair areas. Apparently, most comments from visitors have been about the comfort of the seat padding, and so I really hope there will be improvements made to First Class at the very least.
I have been very impressed with the design of the luggage racks - they seem to be well-proportioned and in the right places. I understand the finished products of these may, however, have slight changes. Bearing in mind the passengers from the two airports en-route, as well as St Pancras, finding these & stowing luggage quickly is an absolute priority.
And a word about the grab handles. Due to the design of the ceiling, unfortunately there are limited mounting points for these. I suspect the central "totem" grab rail in the each vestibule may have to receive some additional bars/rails, but other than that, I'm really not sure what can be done.
The onboard CIS system is going to be pretty clever and versatile, and probably very useful for visitors to the capital, in particular. It is not the finished version, as has been stated, and there have been a number of comments which I think may lead to fairly visible changes - including shifting the analogue clock to a digital format, perhaps.