I would like to get.
1.) Better combat with swords.
2.) More range weapons. I usually get stoned or shot by underground mobs. Cant even survive temporal storm early in game.
3.) More mystery content (like resonance archive)
4.) More advanced tools. Steel age shouldn't be last. If we have gold / silver / copper lets add simple electronic.
5.) Trophies/Artefacts. I really like to explore and collect some artefacts. Something what mod "Better Ruins" have.
6.) Better caves.
7.) Another dimension (like nether in MC) but i heard that it is in the game already. Pls dont spoil it to me.
8.) More bioms.
9.) Potions for boost (herbs)
10.) Rare mythical creatures.
11.) Fishing
12.) Special events (not only temporal storm)
13.) Real usage of rift (that void what make noise), so far it drains only sanity