It was a sad day when architects were allowed to become dominant in station design. The rot really became noticeable with the Jubilee Line Extension. When the Victoria Line was done in the late 1960s great efforts were made in its alignment etc to minimise connecting time, it's full of cross-platform connections and the like. The JLE went to the opposite extreme and put the platforms, it seems, as far away from existing lines as they could, but the effectively separate station meant they could scoop up a whole raft of architectural design awards from their mates.
At West Ham the Jubilee platform (island) is effectively underneath the District platform (island). One set of stairs would be great. Instead it requires three separate sets of stairs, two with escalators, and big overlong interchange passages to do a Down-Along-Up-Along-Down between the two. Needless to say the architect scooped awards for their "wonderful" design :roll:
What utter rot.
At Westminster, the lines had to be deep due to the river. The access cmes right straight past the SSL
At Waterloo, the lines had to cross the existing lines at right angles. Anything else would involve very odd snaking. So they had to be very deep.
At London bridge, any attempt to align for cross platform with the Northern would mean more building under the river, which is frowned upon apart from required crossings
At Canada Water, the JLE access is shared with the access to one of the ELL platforms
Canary Wharf is in a dried out and then filled in (with building) dock bed. The towers had already been built, so it had to miss the foundations. This explains the interactions with the DLR
Canning Town is directly under the busier of the DLR platforms. At the time, the Stratford branch was the unloved North Woolwich line. Rearranging everything here, and all the way to Stratford, for cross platform interchange would not have made economic sense, especially as there still wouldn't have been cross-platform at Stratford and a flyover would have been needed just south of there.
Which brings us to the absolute nonsense you spout about West Ham.
The LTS platforms (the District is the Metro tracks of the LTS) are east of Manor Road. By the time the lines are over the Jubilee and DLR, they've narrowed almost completely back together. But that's OK, because the Jubilee and DLR platforms are to the south of the bridge, with the only thing between the tracks here being the pillars of the bridge.
Your suggestion would require the bridge of the LTS over the ECR lines to be entirely rebuilt in order to fit the access in. You'd then need to find a different route for the access from the main station building to the not very wide LTS platforms (not really wide enough to accommodate stairs mid platform).
So, rather than entirely rebuild the LTS station with new bridges over Manor Road and the old ECR lines plus wider island platforms, they compromised by simply building an over bridge for the ECR platforms that passed over Manor Road and joined to the LTS concourse.
This is way off topic, but then so was your rant against "architect led design". I'm not even architect, and do get annoyed when they stick their oar in where they're not welcome, but the JLE is not one of those places.