The integrated terminal with domestic at the eastern end of terminal 2 was announced in 2017. This isn't new.
The northern runway will be mostly domestic/regional operations.
Correct it's not new. If my memory serves me correctly it pre dates 2017 and 2014 by a big margin.
If you look at the taxiway layout and the location of the second runway, building the domestic terminal to the east as with the current proposal doesn't make any sense. My hazy memory of the original proposal put the domestic terminal to the west or north west of the international terminal closer to the northern runway, thus fitting in with the taxyway layout.
By putting the domestic terminal where they're proposing tells me they have no intention of progressing the second runway anytime in the next 30 or so years.
You're reading too much into it. They are positioning the terminal the way they are due to what they have already and how they will build the baggage system. Doing it the way they have means they can get a lot of space and passenger flow efficiencies from a common check in area for domestic and international. It reduces the cost of the build and will be much more efficient to operate as a fully integrated terminal. Putting domestic to the north would be effectively replicating what they have now which is two completely separate terminals.
It's not ideal with the taxi way but it's a brownfields development so they are constrained by the current footprint.