Is it possible to give a weapon in TES IV more than one enchantment? If so, how do I do it, and what are your personal recommendations for weapon/enchantment combinations for a warrior type character, destinated to apply maximum damage (balanced to hurt magical creatures like ghosts as much as non magical creatures like humans)?
While you can find (and eventually enchant!) weapons with multiple enchantments, weapons in Oblivion only have two states: enchanted, and unenchanted. Once enchanted, weapons cannot be un-enchanted, and there is no way to add/subtract abilities, charge size, or effect magnitude after the initial enchantment.
If you haven't already, I'd suggest you look into the Enchanting guide at the unofficial elder scrolls wiki. The wiki also contains a list of "Useful Enchantments" which sounds like it might be useful for your purposes.