Hopping on the bandwagon re: how would we obtain a new heart-engine in Act 3 and had this idea that after Gortash, we could have a silent continuation (read: doesn't show up as a next objective until triggered by said event) of the heart quest where we'd:

-Have to find Dammon, hopefully fixed and unbugged now, at the infernal forge in BG
- Karlach would say something about feeling hopeless and so angry because turns out Gortash sold her to Zariel because she could withstand the pain and peril of the prototype engine - which turns out was later used to make the engines in the Steel Watchers
- Dammon had no idea and his brain cogs start ticking, he'd ask us to bring a SW engine to him for studies and dismantling
- We either have one already or need to fetch it, depending on forge status maybe? Could pick it there
- Bringing it back to Dammon he could try to figure out how to implement the finalized engine model into Karlach
- It turns out to be quite risky but if we have saved the Gondians, we'd have a higher chance/instant success rate to make it happen
- Fetch a Gondian or if the quest with them gets a new reward for saving them, helping us help Dammon
- Dammon with all the tools at hand figures out a Karlach Heart Engine 2.0
- Up comes the medicine check. Should be quite high to succeed, or a three parter where it goes from 10 to 15 to 20. There has to be some healing spells/restorative spells going since she'd be without a heart for a moment, or we could skip that altogether and have Dammon add parts/coolant/alloy to the existing engine directly in her chest. Trickier but she remains alive throughout the entire session.
-Heart cooled off, Karlach's story comes to a nice end. She started off as a sold prototype host, came back to use the stuff that was taken from her to get a new life, her dear "heart" back but in a new, better way.

Bonus: if Karlach hasn't romanced anyone she could opt in to further flirt with/kiss Dammon. Know tons of fans who'd dig the duo getting together or at least Dammon getting something for his hard work.

NO NEED FOR TRAGEDY, LARIAN.