Disaster #1 If You Couldn't Jump. You could trap someone with water 1 way blocks also you could only build 2 blocks up. To Get Around It you could use slabs,ladders,horses/pigs

Disaster #2 If creepers blew up 10 times bigger. Your house could blow up big. there are not ways to get around it but here is a way to get a advantage. You could make a good mob farm easy to kill with water on the bottom

Disaster #3 If Wood never existed. You could never break stone or other things. To get around it put cheat mode on

Disaster #4 If dirt was replaced with TNT. Lava = No More Of your World. To get around it build up in the sky

Disaster #5 If You Couldn't Mine Or Craft. Makes the game ussless.

Just hope any of these don't happen... Its 0000000000.1%