We want to be as close to save everything as makes sense, but definitely want to make sure we're saving things like quest state, player location, "trap" states (on/off and pressure pad state) and things like that. I.e., the goal is to get as much of the stuff that matters as possible. There may be somethings like state shards of broken pottery or just some object positioning in general that might not make it in, but hopefully it's mostly stuff that won't really effect game play or play through.
This prioritization seems right to me. Add to the savelist first any data directly connected to the player character, then important world state changed by the player -- the rest is negotiable. (I am going to indulge in one "I did tell you guys over three years ago and a bunch of times since that this was vital"

, but it sounds like y'all are on a good path now.)
I do still have a few questions, if that's OK:
1. I didn't see any mention in your list of NPCs. Do NPCs, once killed by any source, stay dead? Does this include characters in Marcaul? Should corpse objects be included in what's saved? "No" might be OK, but what about if there's a loot item associated with their corpse? When a game is reloaded, should UA automatically spawn replacement NPCs for unnamed slain NPCs? Or is it OK to let the player empty out a level (no respawning NPCs after reloading) since the level will be stocked with different NPCs when the player goes back there with a new quest?
2. In your current internal testing of the latest save facility, how fast is it to complete a save in a large, well-explored area? And how fast is it to load a late-game save?
I can appreciate that you may not have gotten to optimizing your save system yet, but I'm still curious what kind of times you're seeing. If saving takes a few seconds for people running normal hardware, great; if whacking the Save button on a high-end machine takes 30+ seconds to complete, I suspect many players will politely explain that they would prefer a more speedy solution.
I could be wrong about the "politely" part.
3. Finally, when the build with the shiny new Save function is released, will it allow us to bind this function to a key? Being able to bind "load the last save" to a key would also be appreciated.
Regarding the team, most of them are still on it full time working through the updates. The original plan was to have people start rolling on to DLC now and a few peel off for future project concepting that any developer would normally do. But given where the game is we feel it's more important to update and improve UA now, other stuff later. It's better for our fans, for our brand and for each of our own psyches.
Thank you. In your shoes I'd be super-eager to work on DLC, or consult on SS3, or start the fun of brainstorming the design of a whole new game. That you're focused first on improving the quality of your first major game speaks well of everyone at OSE.