I love the idea of new animals, I love the idea of flint and steel, I love the idea of a way to cook that's a bit more advanced than just a campfire.
I love the idea of a rowboat that can serve as a middle ground between sailboat and raft. Horses, cattle species (buffalo, bison, yak), seals or blubbery animals in northern temperatures. I would like an earlier game way of warding off drifters from your base that isn't just light based like "popular block game" (perhaps something superstitious like religious trinkets or talismans?). Adding the thing that mod does that lets you pick up and move anvils + similar blocks and for the love of all that is holy adding that fish trap line mod to base game (living any temperature north of temperate is near impossible without it).
BUT the dejank and bug fixes/stabilizing should take priority in my opinion