Some Ideas
So as I see things, the game hasn't really advanced much in terms of core gameplay. The devs have said they kept it simple on purpose because of newer players diving into a game with a ludicrous amount of content around now. I get this, and with respect this is a good reason. It feels like there could be some more stretching though, that doesn't over-complicate the game but adds freshness and unpredictability.
Some ideas have probably been mentioned before, as there has been much discussion on this, but I would just like to highlight some ideas on both variety and quality of life. I'll keep brief for the most part, but let's get started:
1. Portals: Forgotten Ruins introduced one especially interesting feature, and that was the portals, which helped to maneuvre around the map a little better. I'd like to see something similar on all (if not most) maps. This would add an extra dimension to gameplay and assist less mobile killers.
2. Traps: The Outlast Trials has various traps from broken glass to chemical vials scattered around their maps, and I feel his would also add variety here. These could be tripwires, traps that release audio queues, or even hinder both killer and survivor. It's just something else to watch out for.
3. Pumpkins (or something similar): By this I mean one aspect I really enjoyed about Halloween are the pumpkins that either give you a boost or hinder. Whilst I'm not expecting pumpkins, it would be good to introduce items that can add a little buff or nerf to characters around the map, which adds to variety. Heck, even have one of the items give away a small amount of Iri Shards on a very rare occasion!
4. Map-specific events: We have some small examples of this already, most notably on the Alien map and Midwich map. However, maybe each maps has a small chance of a larger event happening. Below are some examples:
4a. The Walking Dead map: When all gens are done, there is a small chance the "Don't Open Dead Inside" doors will burst open and free some Walkers. These could hamper both survivor and killer, but at the same time make them more a hinderance than an outright chaotic moment.
4b. Raccoon Police Department: Same as above, but have them smash through windows when all gens are done.
4c. Tha MacMillan Estate map with Water Tower: That pod has opened up, but qhat if on occasion it sheds a cloud of those spores, which float around the map, maybe causing the effects the crystal fog vials cause in random pockets for a minute or so.
5. The Weather: Change map weather systems, so during a trial there may be brief showers or lighning and thunder which affects elements such as hindrance, clarity, darkness and so on.
QoL:
1. Killer-related mini buffs/nerfs: Some killers are clearly just better than others, and one of the very few things that were right in thay recent disastrous PTB was some of the effects some killers got to speed buffs or nerfs. This can be applied in general. Using the portal idea from earlier, maybe fast killers take a fraction longer to use portals, or maybe killers more vulnerable to loops could have a small buff to breaking pallets or walls (and in turn perks such as Brutal Strength are amended so having this perk is the same for all killers, adjusting this buffs accordingly).
2. Improved perk allocation: When you buy a new character, all owned characters get the perks straight away at Level 1. That may reduce the grind especially for newer players.
3. Change the current rarities on the Bloodweb. Since maps are less useful than items, add-ons and BP offerings, make it so the rarities of maps is a higher rarity, whilst bring most BP offerings and objects down in rarity (obviously, add-ons like the syringe or Iri Bell for Wraith stays higher, but bring other things such as the Blue rarities down to a green level)
4. Trades. I don't think a marketplace would work because of the ability to just buy tonnes of powerful stuff for BP or weaker items. However, have a basic system where if you have more than say 10 of an item, anything above that can be "traded" for a reduced level of BP (say maybe you get 90% BP back on common items, 80% Uncommon and so on). That way, people can get more BP to progress further and reduce the grind, whilst also making sure people don't stock up purely on good stuff through a marketplace.
5. Bring back killer-designated offerings. Especially for newer players wanting to trial killers, have an offering in place which allows a player to play any killer they do not yet own. Obviously, this killer would be limited to no add-ons and only use the offerings and perks already own, but may allow some to trial a killer, just to see how it works. Maybe offer a BP boost for trialing it. Also, don't have this offering focused on just one killer, but instead allow the player to select any killer they do not own with it.
These are just a few ideas, but I feel there needs to be some freshening up of the options available.