More control over item scarcity and biome generation

- Minecraft with friends is it's most fun when items are scarce when you first spawn in and work together with friends to get gear.

-it would be really cool if the menu had an option to make climbing the gear chain more lengthy.

Some options like:

-odds of trees dropping saplings 0-100%

-Rarity of ores and trees (Having the option to tweak the amount of ores spawn per chunk and at what height)

(same thing with trees, setting the amount they spawn in and maybe at what height. so maybe they spawn in only some mountains)

Maybe these are too much:

-Villager trade level generation [Level 1 / Random / Max level] 

-Time it takes for nature entities to grow (carrots, potatoes, trees...)

-Option to spawn in the nether (in the snapshot how there was many half portals in the default world would work better for the nether only. completing a portal in the nether and creating one in the default world would be a really cool achievement)