The idea's entirely usable, but the blunt answer I could give to that is "been there, playing that". =P
It's a simplification, because there's no angel/human dynamic in the RP I'm thinking of, but I'd still somewhat prefer to avoid splitting technology/magic between factions too strictly. Besides, it seems fairer to me to use
Clarke's 3rd law to balance magic with tech, meaning the latter should be futuristic-ish. Overall numerical advantage doesn't really seem to help much in a RP, in my experience.
And I really don't mind throwing magic and such into a modern day setting; it's just having the general time period, society, and tech-level of generic fantasy settings I'd not particularly want. I do find the word "angel" to be a slight turn-off, though.
...With that said, I'm the only one who's stated preferences so far, and mine aren't really all that strong, so don't feel too obliged to adhere to them. I also note you've not answered your own initial question, and would like to see that changed. ^^
Also, I want to see what others would prefer too. Or is it just Norm and myself who might actually RP here? =P