Hmm.. actually, being able to Feint effectively could be considered something along the lines of a talent, in that it is something that is learned once, but can be applied to almost any melee based skill, with the quality of the feint being dependent upon good one is with a weapon (like how parry is intrinsically (potentially) better with higher skill bonuses).
As I stated before, the main issue that Arioch seems to want to get around is giving the person that the feint is being used against some way or method of avoiding the fate of the feint.
The major problem there is that is a player uses it against a NPC, other NPCs could use it against the PCs, and that is when the uproar really starts.....
Some points to consider (IMO) --
1) The Feint cannot be an automatic success, it has to have some chance of failing or else it will be too powerful - period.
2) The defender should, IMO, be the one who determines whether the feint fails or not.
3) The purpose of the feint is to trick the foe into defending in one area while you attack another. I translate this into removing any benefits of parrying and/or gaining a bonus to your real attack.
To simplify my earlier proposal, try it like this...
CharA & CharB both have OB of 100 and DB of 30.
CharA declares that he is feinting with 30 points, parrying with 30 points and attacking with the remaining 40 OB.
CharB declares that he is parrying with 40 and attacking with the remaining 60 OB.
CharA gets initiative, he does his Feint. CharB must make a Perception roll (the specific skill to be determined by the version of RM being used), using the amount that CharA put into Feinting as a negative modifier.
If the perception fails, CharA makes his attack with a +20 for the surprising direction of the attack (total OB of 60), and CharB has a DB of 30 against the attack (no bonus from parrying).
If the perception succeeds, CharA's attack only has an OB of 40, and CharB has a DB of 70 against the attack because he was not fooled and/or he spotted the real attack in time.
That is as simplified as I think you are going to be able to get it without making it too powerful by granting an ability that essentially cannot be stopped.
One of the most important points, IMO, is that a Feint is an attempt to trick the foe. To me, that means that the foe MUST get a roll to prevent being tricked, be it a RR or a simple perception (personally, I like perception roll better because it then presumes that skilled combatants are likely going to look for such things, which they most likely would.