In a variety of sources including Wikipedia and intrepid You Tubers, there are some in my opinion articles which could offer DLC ideas:
In the NPPC Chernobyl, in addition to the exploded power plant, there were 2 other functioning sites nearby, where if I recall correctly correctly they only closed about 2015, a third generator was never completed, so trains ran and people worked. Chernobyl the town carried on as did nearby Kiev. So an area such as Limansk could be duplicated but with normal life of cars buses people, but called Chernobyl. Hunting equipment stores could be introduced and Chernobyl be a staging area much like the Rookie Village. The difference apart from daily life could be eg places to sell artefacts as a border crossing for to work Chernobyl would be a fiction rather than historical fact. Thus it would be open to whatever modders can think of.
When the explosion in 1986 occurred the Pripyat area was subject to a mass evacuation in buses but the toxic radiation spillage whilst affecting the Ukrainian Zone, was far worse in Belarus and another Zone exists which can be found from You Tubers trips into the area. So a fresh Zone can be made.
One nice touch in Pripyat would be music. For music played throughout the evacuation and was not switched off though I understand is not on now. Perhaps a radio station might be interested?
The Red Forest was a forest which turned red but is now green mainly and some people who owned land there have returned so as with the two female stalkers other safe havens could be introduced. In the Red Forest are mine workings which are very well modelled. Couldn't they be expanded including a possible downward cage from the pithead area ie downwards to a Metro like existence. Or along to some of the labs via transitions.
The area of NPPC Chernobyl in the game has radioactive what seem like dried up canals but this water system was only briefly drained for access to the destroyed reactor's base. There are some fishing YouTube videos set in this area of the Ukraine. In Metro Exodus there are some marvellously animated giant fish, including some called shrimps if I recall correctly. Lobster, squid, sharks could all become monsters if the water system gave alternative access to the NPPC in Stalkersoup.
I hope these few suggestions will be helpful and taken up by DLC modders.