Physics Mod!!!

I am currently making a physics mod. I have just started making it, and i could use a few ideas. Here is what i have so far. All blocks will be affected by gravity, and must be connected to a block with a link to the ground or they will fall. Also, long lines of blocks with only 1 connection at the end will slowly bend and then break. caves occasinally cave in, if there is lots of disturbence. if you go in a small pool of water, the water level will rise a bit. if you hit the ground hard, it will leave a small crater. If you break the bottom block of a tree, the tree will fall over. You might get crushed, so it is a good idea to cut quite a high block. It will usually fall away from you, but sometimes it may fall in a random direction. Probably like a 15% chance of falling in a random direction, but if a mob is like walking into it or something, it is more likely to fall away from the mob. The lower block you cut, the higher chance of it falling in a random direction. Also, you will be able to reinforce blocks with a special item. If they are reinforced, you can't destroy it with normal methods (mainly for SMP) and will have very high blast resistance (you must encase it in TNT to destroy). To destroy it you use a sledghammer, which will be charged like a bow. After several hits, the block will smash, and the nearby blocks may go in a bit, only if it is a weaker material (dirt wood etc) and you have a good hammer (iron diamond). Otherwise it will just smash. Any suggestions? This will be a huge mod, so I need lots of stuff to put in. I will probably upload the first release in a few months. So yeah
SUGGESTIONS PLEASE