Note: I would appreciate the increase of images per post to be something like max 30 (instead of 5, feels very limited especially for fan art posts)
Learning from the Witcher 3:
+Witcher 3 had an excellent
depth in story and its world was immersive due to the extensive attention to story-telling (dialogues, dialects, events, lore, choices etc). I really want to see that in C77 too, even if there is more than one main protagonist that you can choose from.
+
Contracts were a fascinating part of W3. I would like to see similar things in C77 (equivalent of "cases" in a modern setting). The reason why contracts were fascinating was:
1) You didnt know what to expect, sometimes you would encounter a monster never seen before.
2) Your bestiary felt like a Pokedex; the more monsters you slew, the more you would feel proud about it (+the nice and organised categories added to the experience).
For C77 I would expect a "bestiary" to instead list either Factions (based on clan or location), or categorization based on case (if we are talking about cyber-psychosis, I would expect something like a cyberpsychologist's diagnosis, modified to express the differences between levels of danger, severity of psychosis, strengths/weaknesses and lastly intel known. Categorization indicates the "power level" (in anime terms), which makes things more interesting imo. A nice example I can think of is whether the case is an exotic (if you don't what that means, its mainly fashion-ware that makes you look non-human).
+The
world that felt expansive and you couldn't see where the edges of the map were. Also (even if it was a bit rare in W3) the satisfaction when unlocking a new area that you can travel to. I would like to see this on C77 in a similar format, with the addition of a planet view (3 levels of zoom would be preferable: planet - region -local map). The Net can also have its own map with a similar format.
+
Fast travel is needed given the size of W3 (and most likely be needed in C77 too). A thing to note here is that a successful city is a city where the players don't want to use fast -travel, but instead walk/drive at their own pace and explore in the meantime (details below).
+W3
locations felt alive. NPCs did various everyday animations (working, sitting, talking, guarding etc.). They also spoke or mumble as you passed through, while various other sounds filled the atmosphere and made it more vivid and colorful. Going the next step, I would expect more player interaction with its surroundings, like sitting wherever, buying a soda from a vending machine, checking your balance in an ATM, speak with a local for a random subject, be asked by various NPCs things that you have to answer, checking and buying magazines from a store, buying various other items that have various uses (for example aromas, batteries, candles, clothes, eye contacts, audio players, etc.), physically interacting with containers or various objects (like newspaper boxes, doors, windows, car doors, car trucks if any, sewage caps, pump valves, food, drinks etc.)
+W3 had a UI menu where you could see the inside of
containers as UI elements. For C77, I would actually prefer the Dying Light approach where you could actually see the physical mesh of the pickup contained inside whatever you open, and grabbing it shows your character reaching out for it (easier to add investigation options ala LA Noire with this approach).
+
Intimidating enemies and villains. One of the biggest pluses of W3 for me was the awe when you first saw the Wild Hunt and how intimidating they looked. Their armor sfx, their animations, the camera work, the unnatural sounds of their actions that fit perfectly into the mood (like Corentheus hitting his staff in the ground after being impressed by Eskel's strength in the battle of Kaer Morhen. I want to feel the same when I meet the bad guys in C77, or even better feel intimidated by my surroundings knowing the dangers of such a setting. Awe and intimidation.
+
Variety in environments. Now I know realism is a great deal that sometimes goes against the variety of environments and settings, but I really want to see more variety in C77 than W3. It would be cool to see a clear distinction of a location based on its history, fame and its type (combat-zone, luxury street, corporate square, slums, cheap market, expensive market, nature, outlaw streets, industrial, abandoned industrial, abandoned residential, post-nuclear patch-work architecture, old vs new patch-work architecture, class-oriented areas etc.).
+
Skill progress was something I enjoyed in W3, but I feel a different system is needed for C77 as there are more skills to be explored this time around (C2020 is based on skills and not leveling anyway). So no skill levels, just variety in skills. Also, skill growth should be 3 times slower compared to W3, even if there are more in C77. The reason for that is that you can easily get OP and things will start to look easy and dull (if we had the skill generation of W3 into the C20 model). If you slow the progress of skill gain, you allow class-focus and considerable strategy when selecting the way to progress. Also, hard choices have to be made more often, and you make skill gain a considerate milestone that will make a difference and basically matter. On the other hand, be careful of the random evolution effect. If skills are needed completely random (like dialogue etiquettes in Shadowrun), a player will be confused when selecting a new skill, and he will feel bad if he constantly bumps situations where other skills are needed. You need to have him feel good about his choices, no matter what path he takes. I would assume that you also know that the Fallout 4 skill tree is a bad system which limits your skill growth based on leveling and takes away from role playing.
+
Game difficulty for the W3 was just enough for me to enjoy winning and losing, although I found it generally simple. Regarding C77, I would keep the same level of difficulty but raise the difficulty on the complexity of achieving things. For example, in W3 you can beat a monster simply by hitting it multiple times, using spells, using poisons and other combat enhancements. However, none of the previous matter if you are simply adept in combat and you know how to skillfully beat opponents using dodge/parry (not counting exceptions). For C77, I would prefer a more strategic approach on defeating foes that is based on a multitude of factors, or simply things that you have to spot during combat (something like MGS series boss battles or the earlier iterations of the Witcher series). That doesn't mean to make the enemies harder, just smarter to beat.
+
Boosts. W3 had potions, grindstones, mutagens etc. C77 will need something similar in from of consumables, augmentations, accessories, clothing boosts and various conditions (positive and negative). I would really like an extended focus on conditions in fact, with various things that resemble actual human conditions (like stomach ache, dizziness, drunkenness, deprivation from substances, moods, and conditions based on your empathy level).
+
Crafting. Not sure if C77 will need crafting as in W3. It could either be a class thing (techie), or be out completely. I think focus on other mechanics would be more crucial, as realistically you can't craft an item from getting various wires, chips and scrap metal. What I would like to see instead would be specific operations that would require very specific resources to do, like medical surgery (actual surgery, not a progress bar), or electronic repair/ maintenance, electronic upgrade, augmentation surgery, drone and vehicle upgrade and maintenance, and lastly net-running.
+
Collections. Personally I feel collections may change a game from "just fun until you beat the main story" to "post-endgame fun", but they have to be done right. W3 did a great amount of work on making its collections feel unique and meaningful. Bestiary was useful for intel gathering, Gwent card collection was useful for beating harder opponents and monster relics were "okay" given their stat boosts (since a system like that existed, I expected more variety but I can't say I was let down either). For C77, if a safe-house exists, make sure to allow the player to fill it with his memories of his experience: display cases, wall mounts, furniture, things he can buy to further enhance his role-playing. That also falls for anything the player has as his own, from the player appearance, to his guns, to his vehicles and weapons.
I could expand more, but I think my crucial points are already expressed. For reference, here is an extensive and descriptive review of Witcher 3, I used it to form this list.
Video is extremely long btw, I suggest you skip to story part (its a bit descriptive before that).