Ranked Mode, Empty Perk Slot Bonus, Perk Diversity, Ebony Moris and other Ultra Rares
Creating a Casual and a Ranked Mode:
I thought of this as a response to SWF. My suggestion would be to introduce a Casual Mode and a Ranked Mode with an MMR system like League of Legends. Ranked Mode wouldn't allow SWF, but perhaps duoing. Ranked Mode would not allow for Ultra Rare Addons (such as Ebony Moris, Silent Bing Bong, Infinite Tier III Myers, Iridescent Hatchets, etc.). Both modes would offer Bloodpoints, but you can only increase your Rank in Ranked Mode. Matchmaking in Casual Mode would largely be determined by MMR, preventing purposeful deranking for griefing purposes. There would be end of season rewards (Bloodpoints, Shards, or maybe special cosmetics) based on how high you climbed the ladder, giving your Rank more meaning.
Empty Perk Slot Bonus:
For each emply perk slot (item/addon slot too maybe?) you get a stackable bonus to Bloodpoints that match. I think this would allow for an interesting challenge, but you would probably have to have it disabled in Ranked so that those who don't take perks are too much of a burden on your team.
Increasing Perk Build Diversity:
I hate how necessary Self Care and Ruin feel. On top of that are WGLF and BBQ which feels necessary for the BPs, leaving only two slots left for experimentation. (Also... a skilled Nurse with Ruin is just overkill!)
I would change Ruin to something else, and make Gens take longer to complete in general to compensate.
I'm not sure what to do about Self Care... should survivors have the ability to heal themselves? I'm not sure...
There are also a lot of perks that rarely if ever get taken such as: Deja Vu, Slippery Meat, Small Game, No One Left Behind, Up The Ante. And for the Killers: Monsterous Shrine, Predator, Territorial Imperative, Tinkerer. And then there is Decisive Strike and NOED... yikes. DS and NOED are just too strong, especially compared to these other perks. Reworking/rebalancing these perks would breathe new life into the perk meta.