As I said, in my opinion using it as a toolkit and taking what you want/need to craft your setting should work well. The D20 Future book is nothing but a bunch of rules to run a sci-fi D20 game.
Here, here!
That's exactly what I've been saying since I first had a gander at d20 Future. It is NOT a setting book; it is a rule book. You can use
something from it in just about any sci-fi campaign you choose to run. On the other hand, you would be hard-pressed to find a setting in which you could use
all of it.
Since our upcoming campaign setting,
Dawning Star is based on d20 Future from inception, we are using quite a bit of it. But even we are not using all of it. For example, unless something drastic changes, I'm fairly certain we won't be incorporating mecha because it doesn't fit the parameters of the setting. (Perhaps if the military-run
Arrowhead had been the ship that made it to Eos, hmmm....)
Long story short, you need to decide which elements fit your particular campaign, which is pretty much what a GM routinely needs to do, right?