Just read this version of the ending. Was skeptical at first, but admittedly this guy's writing is pretty good. Though all the extra content required makes it a bit untenable.
In short:
There's bad, medium and good endings dependent on your EMS score. One problem is that the good ending is a little too good; the fight on Earth goes very smoothly. With the worst ending, Shepard doesn't even make it up the beam.
Once Shepard gets up the beam and finishes the dialogue with the Illusive Man, Harbinger assumes control of TIM's body and 'supercharges' him, and there's a climactic boss fight. Once you kill TIM, Harbinger also dies for some reason.
The Star Child is then replaced with the Prothean VI you meet on Ilos in ME1 (Vigil), who appears and tells you about the reapers based on his studies of them (this version of the VI being a newer one with more information).
It turns out the Crucible is not a weapon, but a power source containing lots of dark energy. And Shepard is the catalyst (which makes a lot of sense in context) who can choose Destroy, Control or Synthesis as usual. In this version, Destroy is automatically picked if you're a paragon (get rid of reapers), Control is renegade (take their power for yourself) and Synthesis is for if you played an in-betweeny Shepard. Synthesis is portrayed here as being the inferior choice that Shepard resigns his/herself to as there is no other way they can foresee; you even have the option here (unlike the other two) to back out and get the "refuse ending" introduced in the extended cut.
In the good & medium endings, Shepard survives.
After all that, there's hours of epilogues. The writer even suggests providing the player with a kind of gallery, so they can watch each epilogue (one for almost every important character in the game) in any order, pause them and come back, etc.
Here's a list of the characters he writes epilogues for:
? Garrus
? Tali
? Kaiden
? Ashley
? James
? Liara
? Javik
? Cortez
? Ken & Gabby
? Engineer Adams
? Dr. Chakwas
? Dr. Michel
? Allers
? Khalisah
? Miranda
? Jack
? Major Kirrahe
? Admiral Hackett
? Primarch Victus
? Kasumi
? Zaeed
? Mordin
? Maelon
? Padok Wiks
? Falare
? Jacob & Brynn
? Aria
? Grunt
? Samara
? Kelly
? Eve (Bakara)
? Rachni
? Wrex
? Krogan Warlord
? Wreav
? Oriana
? Geth
? Admiral Koris
? Admiral Xen
? Admiral Gerrel
? Admiral Raan
? Major Coats
? Kahlee sanders
? Thane
? Morinth
And each one varies depending on whether you get a good, medium or bad version of the Destroy, Control or Synthesis ending. These are also in addition to the main epilogue. It's really over-the-top.