Infections, bruises, etc would be immersive - but I feel ultimately would boil down to just more healing-management (which is less action, more tedium). There are some fun ways to tackle this, however.
DISEASES:
…could be fun. When ARK introduced diseases, one of our members got infected - and then spread it to the rest of us - and it became “a thing” to be “that diseased tribe”.
It’s worth noting that diseases weren’t strictly negative - I remember our illness gave us significant penalties to strength/encumbrance, etc BUT boosted our running speed. So we weren’t a universally weaker tribe - it was a deliberate “rite of passage” to join us, and we adjusted our battlefield tactics (as lightly-armored skirmishers/runners).
ALSO, disease could be fun for raids - as (in the medieval tactic), we would grab a diseased animal (usually a chicken) or a kamikaze tribemate and airdrop them into enemy fortifications. Even after the vector was killed, whoever got close to the corpse risked infection (and then spread it). The result was our lightly-armored runner/skirmishers could rush in while their heavily-armored soldiers were suddenly sick and overencumbered (and desperately trying to shed gear) or overheating (and trying to get out of their own armor). Imagine tribes going to different parts of the map - in pursuit of rare diseases - specifically to then infect other regions.
NATURAL DISASTERS
The sandstorm is easily my favorite mechanic in a game - because when you first get hints that it’s coming, it throws all combat norms out the window. No matter the fight, you usually put aside your weapon and run. You can’t just climb a rock to escape combat (because going up usually means less cover against the storm). And even if you have a mask to protect yourself, it’s thrilling to hear things come for you (and not see them due to the dust).
How about hailstorms?
You could differentiate it from a sandstorm by (a) the damage is not guaranteed but (b) if one hits you, the damage is more severe, especially without a helm? Instead of being blinded by sand, perhaps the ice creates a % chance to slip and fall.
How about whirlwinds or tornados?
Instead of damage, the effect would be to toss actors (players and NPCs/mobs) around. Perhaps damage to weaker (thatch) structures. Local trees, etc all break into branches. Higher strength (or whatever) would let you resist. (I live in Hurricane territory and - although dangerous - it can be fun outside during one of the weaker ones.)
How about tremors?
Hugging the cliffs is often a safety tactic - but what if some areas had tremors that caused rocks to tumble and avalanches to flow?
NOTE - none of these ideas are solely about making life difficult… but the affect combat because of how the new conditions of the environment force us to change tactics. I find the sandstorm super exciting precisely because it forces me to re-strategize otherwise rote situations.
And if players could somehow trigger effects, that could be crazy fun. Maybe similar to Purges, there’s an invisible bar to track when environment disasters spawn? So summoning Sag boosts the tornado track (giant wings), summoning Ymir boosts avalanche/tremor chance, etc. It’s not something any clan can control - merely a convenient trigger (I’m already imagining clans using sandstorms as cover for invasions).
