There will be no "legal" way you can create such item for Multiplayer games, which enforce "legal items". Adding all these bonuses to that robe will give it a much higher level requirement, then lvl 20, so you just can't wear it in "legal" games.
If it's "open for anything" game, then there's really no point. After you make that robe, the melee person will make a sword which shoots out lightning bolts and what not else, and still kill you in close combat. Then you make yet better robe, he makes better sword.. Endless.
Not to mention - you are NOT supposed to win close combat melee fight, as a spellcaster, against a melee char, EVER. If you let melee char near you, then you did something wrong. You have to keep your distance and use your spells. There's spells which can make one immobile too, use these on him and then shoot from distance. I have yet to see any range limits on spells or ranged weapons in NWN...
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