Since I haven't had time to play for a while, I decided to already post all that I personally think could be improved. Prepare for a wall of text though. Plus there might be more.
I understand that some of those, if not most, would require a decent amount of work, which most probably won't be possible, given Infusion. With this in mind, I hope that at least some of those will come in handy with the next project.
All suggestions should be fairly spoiler-free.
UI:
1. A toggle in options to auto open inventory on looting/bartering/crafting would be great.
2. By the same token, an option to auto-turn the inventory screen off when cancelling trade would be great too.
3. Adding some hover tooltips over options in the menu as to what they mean.
4. All dialogue options can be accessed through keys 1-9, except rare cases of 10 or more dialogue lines. The 10th one could react to key 0. Maybe also - and = keys for options 11 and 12.
5. I reckon a more visually clear way to turn off the F1 screen would be nice. In addition, allowing it to close by pressing F1 again would be nice as well.
6. Crafting window: perhaps move the "Create" button so that it's under the slots for materials.
7. While maybe live-resizing of windows is out of the question, but perhaps increasing the inventory window of containers, depending on the number of contents, would be possible?
8. There's no difference in terms of scraps yield if you recycle a gun that's loaded, and when you unload it. I reckon the most sensible solution would be to automatically unload the gun while it's recycled
9. Hopefully I'm not missing any setting here, but the ability to move around the "world map" (like click and drag to move around) would be amazing.
10. A new hotkey to automatically unequip both weapons and belt items.
11. Maybe different ways to sort items? At this point, I can tell that the current sorting order is roughly item type -> item name -> item value. It gets a little bit complicated with guns, since, I believe, the frame is also considered. Would it be possible to add one more sorting type, a plain old "sort by value" in descending order?
12. Using the fishing rod is cumbersome, UI-wise. The only sensible way to use it is to open the inventory and to activate it from there. Even if one moves it to the action bar, it will disappear from it once it's deployed, and I think it should remain in the action bar, until it's removed, or the fishing rod is reclaimed.
13. Mass recycling of items would be nice. Maybe 8 items at a time.
GAMEPLAY:
14. It might be a nice thing for immersion if Joe's Special also came as a proper consumable. Pricey enough too. Maybe a quest to travel around Underrail and collect ingredients, rewarding a unique feat?
15. Amusing Sophie. One of my attempts to amuse her (before I found the right one) was to bring the head of The Beast to show her, hoping I'd be able to tell her of the fight. The game didn't give me the option, but maybe it could be made into one? Maybe other similar "monstery" items could work, like regalia of the Rat King, or any other ways of finishing this part of the quest?
16. Maybe it would be possible to introduce a skip to all the arena annoucement talk during each fight?
17. In some caves, some exits are notoriously difficult to spot (especially south east passages), unless you manually hover over them. as the red exit field is obstructed by the wall. Maybe the exit field could be extended to be in view?
18. I suppose Sprint could be made usable in Stealth (only when not in combat), but would automatically break it.
19. When you shoot ice and acid barrels (I assume rocks too and other similar shootable objects, I didn't pay attention to those), I suppose they could have different portraits, rather than just a black human silhouette.
20. When some house improvement dialogues with Jyles are exhausted (like basement upgrades), maybe they could be disabled altogether?
21. Assigning floor numbers in SGS (or anywhere else, where elevators have numbered floors) to specific numbers in dialogue choice permanently. If you're on that floor, there would be a missing dialogue number, or that number would show "Nowhere".
22. Maybe it could be made possible to remove the head of a certain bad animal from its mount in a certain household (and place it back), just as an option?
23. Is there a reason the action bar only goes to 9? The only non-technical, plausible reason I can think of is screen estate on low resolutions (I haven't tried those myself), but maybe on high ones it could be expanded to 0, - and =?
24. A new dialogue option and possibility to fix broken floor tiles in player's house. Yeah, those tiles mildly drive me nuts.
25. At some point, a certain handsome informant in Core City says that we owe them a Root Soda for some piece of info. It would actually be nice to be able to give him one later.
26. The "boulder-splash" cutscene in Crimson Meadow Horticulture feels really too long. I'm not sure it's supposed to describe the whole process, but rather be symbollic. One rumble->splash would be enough, I reckon.
27. A small remark: using a jet ski without the key will invoke a message that includes some lockpicking info. Given that one can't use lockpicks on them, what's the purpose?
IMMERSION:
28. I suppose it could be a nice touch immersion-wise, if the screens that show "Gauntlet" in Core City would occassionally switch to showing some info once you finish the quest about a certain "demigod". Maybe not permanently (since JKK would probably notice and fix that asap), but until the player leaves the Core City map unit completely.
29. During one of my Arena matches, a burst spray destroyed the camera. During the next game, the camera was there. Now, no big deal, but maybe it could be slightly expanded upon. Maybe, the moment a camera is destroyed, the announcer could say sth like "We'll have to fix that", or that the camera doesn't appear during consecutive runs.
30. Maybe it could be worth expanding upon Anastasia's dialogue when she tells the story behind her health situation, to mention a certain chemical gun-wielding trio? I know she says "we were told it's 'SOMEONE (BUT NOT THE CHEMICAL TEAM)", but the circumstances of her health deterioration fit a lot more with said "chemical brothers". Maybe a slight retcon and expansion to this character? Maybe it could be somehow explained that it might have been them (if alive), and if they're already dead, maybe the player could give her some solace?
31. Maybe reworking the description of Huxkey? First of all, there's a small issue and it should say "(...)combined with a high-end hacking device." Additionally, I would somewhat emphasize that those lockpicks aren't reusable. Maybe adding a bit of info that those lockpicks are from supersteel or sth?
32. Immersion-wise, it might be a good idea to tell Constantine about it once the player decides to lay waste to some crazies that are heavily into zappy rock-climbing.
