Ageing Mobs

This mod will allow certain mobs to age under certain conditions, when they reach this condition they will transform in to a different mob.

Mobs that can age by default using this mod:

Creeper to Charged Creeper
Zombie to Husk
Husk to Zombie
Baby Zombie to Zombie (also Baby Husk to Husk)
Villager to Vindicator
Vindicator to Evoker
Guardian to Elder Guardian
Endermite to Shulker
Skeleton to Stray
Stray to Skeleton
Rabbit to Killer Rabbit
Cow to Mooshroom
Bat to Vex

Nether exclusive transformations:

Skeleton to bow wielding Wither Skeleton
Slime to Magma Cube

How can each mob transform:

Creepers slowly age in thunderstorms, when they reach a certain age they can transform in to a charged creeper
Zombie ages in hot biomes and will eventually change in to a husk
Husks will age in cold biomes and will eventually turn in to a zombie
Baby zombies will age over time eventually allowing them to grow up
Villagers that are kept in dark places for to long will age and eventually turn in to a vindicator, their age will decrease while they are in light
Vindicators with magical items near them (Bookshelves, Brewing stands and enchantment tables by default) will age and eventually turn in to a evoker
Guardians will age over time and after a long time they will turn in to a elder guardian
endermites will age over time, when you name these creatures they can stay alive much longer and will allow them to age to a point where they can burry themselves in purpur blocks, allowing the purpur block to eventually turn in to a shulker
Skeletons in cold biomes will age and over time freeze in to a stray
Strays will age in hot biomes this allows them to convert in to a skeleton
rabbits left alone in darkness will allow them to age until they reach the feared age and turn in to a killer rabbit
Cows on top of Mycelium or with mushrooms nearby will age over time and eventually turn in to mooshrooms
bats will slowly age over time until they eventually transform in to a vex, Be careful while caving!

Nether transformations

Skeletons in the nether will age and eventually burn up to a wither skeleton, their bow still seems to be intact
Slimes that found their way to the nether will age and over time adapt to the heat of the nether allowing them to turn in to magma cube