Well i have looked over many people's attempts at creating Eeveelutions and i think that this is a proper way of going about it!
Steel- Chromeon - Evolution Holding Steel Coat, Level Up In A Building
Ghost- Ghouleon - Derived From Ghoul, Evolves by Leveling Up at EXACTLY 12:00 MIDNIGHT whilst holding (Spell Tag)
Flying- Aereon Derived obviously from AIR! and evolves with 1st Pokemon In Party is a Flying Type, knows Fly, and Levels Up.
Poison- Toxeon, Derived from Toxic, Evolves only after battling a Poison Pokemon and Leveling Up
Ground- Crusteon, Derived from Earth's Crust, Evolves While Underground, In Bases, Etc. After Leveling Up
Bug- Secteon, Obviously derived from insect, Evolves whilst Battling A Pokemon Found using the Honey Method, and Leveling Up
Rock- Bouldeon, Derived from Boulder, and Evolves while holding Hard Rock, and Leveling Up
Dragon- Drakeon, Derived from drake, Evolves whilst holding dragon Scale, and Battling a Dragon type and Leveling Up.
Fighting- Battalion, Derived from Battle, Evolves when winning a Tough Master Contest, and holding Black Belt
Well thats my personal Opinion?
Anyone like it?