I think the primary complaints about Co-op TT is;
- There is not enough room to explore.
- This one is caused primarily by the Draw range of the Hosting computer/console.
- Crafting is not available.
- I think this is caused by the inability of the host to Share "Crafting Events" without Crashing.
I have no Idea how to fix these on the Coding side of things. Having a designated Server to provide a "World Host" is problematic as the Game is Process hungry as it is tracking every loose bit of of player usable resources (Blocks, Chunks, enemy techs) Within the Shared draw range of the players. Take the current inborn game lag in FPS, and divide by the number of players.