Gamerule options

Add options at the end of certain gamerules to allow them to be set more specifically

e.g. -> /gamerule mobGriefing false minecraft:creeper

The "minecraft:creeper" at the end would just be the specified thing that is affected, so in this example it would only disable mobGriefing for Creepers, or maybe for lavaSourceConversion you could say 9 for 9 blocks minimum to spread. This would allow for more flexibility and would improve the game in a tiny way.

This would also be incorporated for creating worlds.