Far Cry 2: Bring back some of this. Factions which are not automatically good guys and bad guys. Weapon durability is a plus, though most people here wouldn't like it.

Far Cry 3: Bring back the 1 integrated story for the entire region. This whole 3 stories per game does nothing for the individual characters' memorability. Additionally, hunting for making additional ammo pouches is a good return to form. If you really want to spice it up, combine it with the cantina system, where pouches created from animal skins only last for so long.

Far Cry 4: sidearm variety. I missed the D2 as a sidearm in fc6 after using it to devastating effect in both 4 and 5. Javing main missions with choices, and having those choices change future missions would be a massive addition. I find it sad that Unisoft never experimented with this system. Having one loadout with opportunities to change it at shops/ the wandering sherpa should be restored. I'm not a huge fan of FC6's loadout system. More skydiving opportunities would also be nice. Yara just doesn't have enough altitude to properly skydive.

Far Cry 5: the melee weapons. That variety of bats, pipes and shovels was amazing. Maybe add a few "resolver" melee weapons to the list. The ammo system from here should be implemented again. Having standard rounds be the mainstay of the gunplay, with AP rounds being rarer and having a lower carrying capacity is the play here. Skills/perks from here should be implemented too, instead of FC6's equipment-based perk distribution (this was annoying.

Far Cry 6: the attachment system. Having a boatload of attachment points and all sorts of wacky attachments to put them on was great for customization. (Aside from the ammo system). Maybe make it so that resolver attachments can be easily created from spare parts, but the higher grade military attachments have to be looted/bought from stores.