My understanding is that the most most important point of any project isn't just building and labour cost
but also minimising lost revenue due to the potential of capacity reduction.
So there's a really strong argument to do what's currently happening at Anfield adding a 2nd tier to the away end.
Basically we block off the land behind the Kop and do much of the building work on there, so initially there's no actual reduction on capacity.
As the project gets closer to completion then a section (maybe 2,000 seats) right at the back of the Kop would need blocking off with final works done during the Summer.
So the vast bulk of the Kop would remain fully operational throughout the modernisation work.
As the Kop has the worse facilities in the whole ground it does really need doing sooner or later.
but as mentioned earlier regards safe standing in the short term an answer might be the trial it in the Kop corner.