Marvel Chronology Project

FB #1, 2420

Ultimate Ultron
Spider-Man
Black Widow
Captain America
Star Brand
Hawkeye
Wolverine
Robo Cop
She-Hulk?

Later

Ultrons

Later

Ultrons
The Sorcerer Supreme

Later

Bio-Slaves

Later

Thor
Ultron version of Captain America, Hawkeye, Gorgon, Black Widow
Ultron

Main Story

Year 20XX

Golden Skull and his pirates
Captain America (Danielle Cage)

Present Day

Black Widow
Vision

Year 2420

Doctor Doom Black Widow (time displaced from the present)
Vision (time displaced from the present)
Thor (Foster, time displaced from the future)
Thor (Odinson, time displaced from the past)
Iron Man (Rhodes, time displaced from the past)
Captain America (Danielle Cage, time displaced from 20XX)
Hulk (time displaced from unknown era)
free humans that Doom has aided including Merek

Later

Ultons assigned to Avengers Tower
Vision (time displaced from the present)
Iron Man (Rhodes, time displaced from the past)
Ultron Captain America
Ultron Spider-Woman
Ultron Hawkeye
Bio-Slaves
Black Widow (time displaced from the present)
Hulk (time displaced from unknown era)
Captain America (Danielle Cage, time displaced from 20XX)
Ultron Black Widow
Thor (Foster, time displaced from the future)
Thor (Odinson, time displaced from the past)
Thor
All-Father Ultron
.

Hulk's from shortly after Incredible Hulk v1 #6.

Rhodes is from his first stint as IM, pre IM 200.

She-Thor's from the relatively near future, and so may become placeable after we see the ANAD Avengers setup. (She and Vision have been teammates for a bit by this point).

As revealed later, Thor is plucked from a point in time during his battle with the Midgard Serpent, I'd say between Thor 379 and 380 to make it simple.