Though it is very very unlikely the game would update, i thought i would post a suggestion about custom rules.
What i was thinking was, for when you are using custom rules. you should have the full ability to customize settings based on your desire instead of pre-made settings. take for example health, you should be able to customize how many hitpoints it takes when you get attacked or hurt. (ex: 55/100) and so on.
Some settings will not be affected by this change (for obvious reasons), but a lot of settings will. you would even have the option to set how long day and night cycles are around the world. for example you could set it to 2 hour day times, and 4 hour night times, and so on.
And when generating worlds, you should be able to set the temperature to whatever you want (lets say -200 fahrenheit). and you should also be able to set how long or short oceans should be (based on a block to block factor). and so on.
I do hope you get the point on where i am going.