Some suggestions I have,
-Adult Tallbirds hatched naturally should-well, they should hatch faster, and-each new Tallbird should make it's own nest. The Tallbirds would keep reproducing and eventually their would be tons of them; the only way to get rid of them would be to destroy the nests, at the sacrifice of the eggs they spawn.
-Spider Queens that spawn should leave their original location and travel through areas the player has explored, specifically close-ish to the player's current location-and they would destroy anything and kill anything they see as they go along.
-Often, new Spider Dens should spawn near Tier 3 Spider Dens.
-Once the amount of hounds that spawn at once caps, their stats should largely increase after each attack
-The spiders in Tier 3 Spider Dens should "upgrade"; if the Den is left untouched,eventually every spider in
the Den would become a Spider warrior.
-More stuff like the "Night Hand" that puts out fires; It's terrifying at first, but the affect wears off fasand it begins to feel stale. I would love to have more stuff like that, preferably shadow creatures, that attack randomly at night.
-Eventually, any Berry bushes remaining would rot, and be replaced by new Berry Bushes, though spawning at a lesser frequency than initial spawn, the same as default if Berries are set to "Lots" in the menu, and none if set to "less."After this event has happened at least four times, no more berry bushes.
TL:DR: The difficulty should increase as the don't-starve days go on and stay the same early on,since inexperienced players probably wouldn't survive that long anyway.