I echo the call for Anger of Angels if you want a truly celestial campaign. However if you have d20 Modern and Urban Arcana (Menace Manual would help too) a little effort will get you the game you want without having to spend any money. Urban Arcana has Aasimar and Tieflings. If you don't really consider them powerful enough for Angels and Demons grant them some spell like abilities and extra feats at character creation, perhaps a Smite ability or supernatural senses. That and lots of flavor text will go along way.
I realize its not exactly what you asked for, but if you have any of the books you mentioned in your first post, the ones you weren't sure about mechanically, you can borrow the setting, world, and plot from them and import d20 Modern creatures and rules. Altering them cosmetically if need be. From what I have read of both Fallen and In Nomine these kinds of mechanics would cover at least some of the campaign styles available in those worlds.
I have been tossing the idea around of a d20 Modern based expansion for the ongoing war between heaven and hell, and I might be willing to give you some help if you wind up going the way of the homebrew.