These are things that turn into crazy serial killer wall montages... there are so many different versions of events to consider.
A lot of things are dictated by the need to allow for a Marla solo route. In the current alpha, I've expanded a lot of Marla's content and allowed some choices for Liam to make in that regard, but having one of the girls always pushing into a poly relationship limits player choice too much.
Basically, as long as Marla doesn't know abou Lani's racial curse, she will push for poly UNLESS Liam has specifically said he wants a monogamous relationship. If she enters into the relationship before learning abou Lani, she realizes that something is strange about Lani's curse, etc
As for the dungeon expansion, that's on my list. At least partially... I hope to add at least a small amount into the succubus dungeon variations. All of that was written before it was possible to enter into a relationship at all.