You already CAN Starve to death. If you don't eat food for a long period of time that 25 starts ticking down to 1, and then a stiff breeze will kill you.

Constant rain would make it impossible to do most things in any biome that isn't the Swamp.

But Permadeath and always on 2 stars could be a lot of fun. No teleporters is something you can just do on your own already, just don't make them.

I guess if you want constant rain you could just type in the console command that enables it and just leave it alone, it will keep raining until you log out, making you wet the entire time.