The ghost touch property does not help you hit ethereal creatures anyway, only incorporeal.
Incidentally, where does it say that the ghost touch property doesn't apply to ranged weapons? I'm certainly not saying it does, but all I can find are references to people saying that Ghost Touch doesn't apply to bows and the like: I can't actually find where in the rules it says that. Other properties are specifically melee-only or ranged-only, but the only thing indicating that ghost touch doesn't apply to ranged weapons - as far as I can tell - is the lack of a line saying "a ghost touch ranged weapon confers the property on its ammunition", which is hardly conclusive. Admittedly, the Ghost Touch Weapon spell from the Spell Compendium excludes it, but the weapon property entry doesn't seem to.
There could well be an entry somewhere else that I'm not aware of, of course.
If there's nothing definitive, then I see no problems at all with the concept of a bow that makes its arrows able to hit incorporeal (but not ethereal) creatures. Remember: incorporeal creatures are on the Prime Material plane by default, they're just insubstantial. Ethereal creatures are on the Ethereal plane, which is a different kettle of fish.