Here's some suggestions that with little changes can make all the difference
Weather/seasons. Seasons would make a interesting way to make challenges through time in the game. Four seasons, four ground rules:
1º Spring. Berries, plants, Flowers and wild animals all around by increasing their spawning rate. Regular chance of sunny days, lesser wind speed. Dark forest creatures HP regen. Increased spawning rate of monsters of the forest. Stamina ticker +1 or +2. Longer rested status.
2º Summer. Berries, wild seeds, star creatures spawn increased, plantations growth speed, wind speed increased. High rate of sunny days and fog. Feed time decreased. Plains creatures HP regen. HP ticker +1 or +2. Lower ticker damage of could status, wet goes off more quickly.
3º Autumn. Berries, plants, wild animals and forest creatures spawn decreased. Mushrooms and thistle spawn increased. [Future]Mistlands and Meadows creatures HP regen. Stamina ticker -1 or -2 (if receiving higher amounts). Plantations growth speed decreased. Higher rate of lesser treasures (food stocking).
4º Winter. No berries. Plants and wild animals spawn greatly decreased. Mountain and sea creatures HP regen. Wolfs present on dark forest. High rate of rainy or snowing days and storms. Wet and cold status stands longer. HP ticker -1 or -2 (if receiving higher amounts). Plantations lost and the bees are not happy. Have stocking to not be grounded, or pray for lucky looting. Rested status lower duration. Lox/wolf Cape and frost resistance potion to endure mountains.
This might sound insane to some people. But I think it actually makes things more interesting since you'll have to worry about the changes but also benefit for time to time focus on some kind of activities (now is the best time to harvest, or get wolf meat and crystals or get fight and loot this kind of monster). And no need for big changes on the game baseline itself. Also frost resistance potion is basically useless after wolf cape, I think winter (or any other seasons) might ask you to variate your sets and use what before it's marked as trash loot.
Of course I'm going adrift of equilibrated mechanics, but if you get the idea leave a comment and your suggestion.