First of all, I don't like it being compared to a light-saber, even though I imagined it as a glowing semi-transparent blade. The idea is that this blade is nothing more than an extension of the casters aura. A constant stream of manna flowing out of him and only molded it the shape of a sword. The moment the caster releases or ceases to sustain it, the sword dissipates. One good blow to the back of his head could cause enough loss of focus that the spell is dropped. Secondly, this is my third version of this spell, and I've entertained many other concepts on how to restrict its power. One was to make it a metamagic, but I didn't think it seemed like a metamagic. Another idea was to make its duration instant, take the net hits away from the DV and say the spell lasts for (net hits) combat turns until it must be recasted, but again this seemed to far from RAW. I'm also very tempted to make this spell "caster only", or take up that Improved Reflexes suggestion.

Nope, you nailed it. A more complex bullet has a higher OR so would require more hits on say, SnS, then it would on regular ammo. But the fun thing is that the spell only reduces ITNW's power, it doesn't change armor ratings or AP, so even though the spell is harder to cast on SnS it would retain it's halving AP quality.

Oh, and it should read "Net hits" not hits in the spellcasting description. Working off memory I forgot all about OR until you brought it up.

To be honest, that sounds like a special visual and touch-mechanic effect for a basic touch range damaging combat spell to me. Take something like "death touch" and give it the bonus effect that the mage effectively gains +1 reach when using it, describe it with some cool visual effects, and there yah go.

That way you have no new balance issues because every time you hit with it, its a new spellcasting roll & drain resistance test. Might even not change the drain compared to death touch; spell gains some extra drain for the reach, but looses some drain for having the obvious visual effect (which alerts the target), so call it a wash. Keeps it consistent with other spells. (Reach isn't much of a bonus in SR4.)
Of course, this does mean the spell can't affect non living targets (assuming it is mana based combat spell- a physical spell could hurt them just fine, but won't work in astal space). Again, that just makes it consistent with other spells...

My bad again, checked my notebook. It WAS hits and not net hits over the threshold. Net hits would make the spell far too ineffective as a common bullet would still have an OR of 2.

Besides having the OR outright effect the spell besides whether or not it even takes place is a break from typical mechanics IIRC.

This just gets better and better. At least keep the OR!

I'll consider it. On the other hand, maybe I'll just make it up to you by allowing free spirits history with the a guarding spirits to take the Mystic Armour adept power at same cost when you create your next character.

To be honest, that sounds like a special visual and touch-mechanic effect for a basic touch range damaging combat spell to me. Take something like "death touch" and give it the bonus effect that the mage effectively gains +1 reach when using it, describe it with some cool visual effects, and there yah go.

That way you have no new balance issues because every time you hit with it, its a new spellcasting roll & drain resistance test. Might even not change the drain compared to death touch; spell gains some extra drain for the reach, but looses some drain for having the obvious visual effect (which alerts the target), so call it a wash. Keeps it consistent with other spells. (Reach isn't much of a bonus in SR4.)
Of course, this does mean the spell can't affect non living targets (assuming it is mana based combat spell- a physical spell could hurt them just fine, but won't work in astal space). Again, that just makes it consistent with other spells...

With the special effect idea all that would happen is that the vorpal blade would change its looks, become ghostly, fade in and out of reality, or sparkle ominously as you change what you are doing with it.

It also means that it is fully consistent with the rest of the spell casting system, which while it has problems, isn't bad

Seriously, a simple retexture of the Elemental Aura spell makes vastly more sense. I mean, first off, it's already an established spell. Secondly, it makes more sense that this blade that is extended from yourself out of pure mana feels like a natural extention of yourself - hence the Unarmed Skill.