I guess that means that they will open a walkway between C and D, which... good? I guess?

It's still gonna be a mess I think.

T1/T2 complex is sprawling lengthwise, that's not good. To make this sort of thing work, you want a central spine and "ribs" of terminals. Like the trains are in MUC and ZRH. And you want to be able to travel between them cleanly. Currently the train is unclean. and every time you enter it you have to re-clear security. I don't see how they change that. MUC sorts it by having three cars. ZRH sorts it by having the train only be non-Schengen with clean and unclean cars.

At very minimum they need to have 3 zones in the train, is that feasible? Schengen clean, non-Schengen clean and non-Schengen non-clean. Schengen non-clean can use landside buses, if they still exist.

B needs a clean way to transfer that is not the sometimes bus. Or perhaps they can reconfigure it and make entire B Schengen. Or make entire B non-Schengen and move B Schengen operations to T2.
C needs a clean way to enter it in the first place. Currently, unless I missed some recent change, you can't cleanly transfer into C from either Schengen or clean non-Schengen airside.

D/E are not at all integrated...

There's a long way ahead to make this work... if at all possible... maybe with T2 emptied and moved to T3 it can happen.
But I would be certainly not singing the praises before we see the result.