A few gameplay issues to be fixed for any upcoming fallout title and gameplay suggestions.
1) No invisible walls: I only noticed this in New Vegas, but it drove me crazy. If You need an area off limits model the environment so it's of limits.
2) Climbing Ladders: Just climb ladders like in most other games, don't load threw it. For a little flair slide down ladders.
3) Surface sliding: Not being able to move or jump on surfaces while slowly sliding off of them is no good.
4) Vaulting/climbing/jumping: Vaulting over and climbing up objects adds a lot of fun vertical movement. I'd would like to be able to cleverly climb onto a roof.
5) A more intuitive pipboy UI for items: A minor issue really, but grouping items, sorting, icons, something to make it less of a pain to search through.
6) Enhanced crippled limb indicators: 1 leg crippled = limping, both legs crippled = crawling (actually show falling down and adjust cross hair height), Head crippled = greatly reduced vision, arms crippled = shacking cross hairs. The severity of these indicators could be fine tuned for gameplay hardness level or hardcoe mode.
7) Crafting: Not just of special home made weapons, but of armor too. Possibly of regular guns and energy weapons only after unlocking it at a certain area, and only in limited way by limiting production or increasing mats used. Think doing a quest line from gun runners and gaining rep and them letting use a production line or energy weapon equivalent but from Mr. house. Armor isn't very complicated so gather mats (hides, scrap metal, etc.) and crafting shouldn't be a problem just don't allow power armor crafting or follow a similar quest format. Follow the same s.p.e.c.i.a.l. rpg format to affect crafting (repair skill and crafting skill should not be separated) and a entirely new aspect of the game is opened up.
8) Repair: Be able to repair items with mats (scrap metal etc.). Also, change up the item degradation system making it more realistic. Melee and armor should keep the old system, because it makes sense. Guns and energy weapons should have a maintenance system (cleaning/recalibrating respectively). The more you use it the dirtier it gets. After a certain point (50%) you increase the risk of jamming/malfunction which continues at a linear scale until it gets to 0, at which point the weapon suffers a catastrophic jam/malfunction, breaks, and doesn't fire until you repair it which is more complicated than maintenance and requires mats or a similar broken weapon. Weapons you find out in the waste should come in all different levels of dirty and half of found weapons should be broken requiring repair.
9) A few A.I. tweaks: When you first enter an area controlled by a neutral faction, any npc should approach you and direct you where to go. A simple dialogue of "Should you be here" or if this is a quest area "Such and such is looking for you he's over there". Make the A.I. down time a little more realistic and have them interact more with each other.
10) More dialogue outcomes: Just keep or add the stereotypical archetype good, evil, neutral, sarcastic responses to all conversations and have the npc respond accordingly. I'd like to be able to piss someone of so much that they try and kill me on the spot.
11) Quest outcome options: Lots of variety to quest outcomes makes the game fun and replayable. It's ok to be ambiguous with good and evil, but just be creative. More of stuff like npcs swearing vendetta against the player.
12) Source of income: End game source of income from a business. Lots of variety; courier, salvage, store, what ever. It operates autonomously and you stop by to pick up the caps. Make it a quest to find, staff, execute said business. With minimal upkeep and a few surprises (you courier dies mysteriously, your manager is suicidal, a competitor hires ninja assassin to wipe you out.
13) Lots of weapon and armor variety and looks (not just 2 cool looking light armors) .
14) Keep faction reputations.
15) Non-violent and creative gameplay: Not just through dialogue options either, all though mainly, but cool stuff like sabotage, blackmail, bribery, frame ups.
16) Keep it weird and dark, with glimpse of the sun.
17) BE CREATIVE AND FEARLESS: Don't be afraid to change things, add things, remove things, whatever as long as it makes the game better (please don't dumb it down though)