One very important aspect of 3.x is that it is also d20. And if one is playing the default setting with no alteration, (which happens to be Greyhawk, in case any were not aware) then it already includes by default sci-fi elements automatically (see Blackmoor, the Egg of Coot, and the City of the Gods adventure). Which is a roundabout way of justifying the use of d20 Modern, Past, Apocalypse, Future, and more options and items.
Note in d20 Past the feats Sidekick and Minions, which are respectively the Leadership feat's cohort and followers broken out into two sections. The discerning minmaxer, realizing that these are technically different feats could enterprisingly take all three. Especially as no restriction is placed on taking them in relationship with Leadership.
Even Apocalyptic fantasy can fly, after all, if it worked for Shanara, why can't it work for you?