Iron Kingdoms really seems like your best bet, considering it has all you are looking for except these skyships. It also seems to fit the flavor you want - FR or Talislanta with guns and mechs would be pretty incongruous to their themes.
And what exactly do you mean by skyships? Regular boats that fly through the air? Because that wouldn't be IK at all. Make them steam powered, turbine driven dirigibles with a huge green floatstone in the middle that provides all the lift and THAT might work, though.
If that's not what you want, just grab some random firearm rules and drop them in Eberron. It's the campaign where everything fits!