How can you build Ifrit or Shiva as Eidolons?

[RedRobes]

Hey,
I was hoping there were people on here far smarter and wiser than myself. I am about to start playing a summoner in a PathFinder game and really wanted to have an Ifrit-like Eidolon, possibly even changing him to a Shiva or Ramuh if we needed ice or lighting attacks/immunities for a particular part of an adventure.
I've started trying to build him several times, planning what I would add each level, and can't come up with anything I like. Does anyone have a 20 level plan for building the elemental-type summons common to the Final Fantasy games?
I'd like to play as a human, but that's isn't set in stone. Anyway, if you have any suggestions, please let me know. Thanks.

[Der_DWSage]

Well, lessee. You're never going to get the 'pure elemental power' you're probably looking for, but...yeah, I'll take a stab at it. This is assuming you never take Extra Evolution or have a race that grants extra evolution points, so keep that in mind.

Quadrupedal Eidolon.
Level 1 Evolutions:Claws, Pounce, Fire Resistance. (Take the feat Multiattack so you can actually make use of all those attacks.)
Level 2:Reach(Bite)
Level 3:Improved Bite
Level 4:+2 Strength
Level 5:Energy Attack(Fire), remove Improved Bite. (Take the feat Improved Natural Attack(Bite) instead at some point, if the extra range is important to you.)
Level 6:Scent
Level 7:Remove Fire Resistance, take Fire Immunity
Level 8:Remove +2 Strength and Reach(Bite). Take Large size.
Level 9:Bite Evolution (Allowing 1.5x damage on strength) and Reach(Bite)
Level 10:Remove Scent, take Grab(Bite)
Level 11:Tail
Level 12:Tail Slap
Level 13:Remove Tail, Tail Slap, Reach(Bite), and Scent. Take Huge.
Level 14:Flight
Level 15:Scent
Level 16:Magic Attacks
Go on your own from here

There's issues with it, but I figured the main events would be getting Huge size, getting immunity to fire, and dealing extra fire damage. That and, well, I kinda lost interest in statting it out past a certain point. Still, it makes for a decent baseline to play with.