Not really, but I actually thought a FP cost might not be a bad idea - although per scene (Like the Sword of the Cross' ability to ignore a Catch), not per swing - i.e. tapping into the Old Soul or whatever. Alternatively, that could be a way of further discounting it - i.e. you can purchase a cheaper version if it only applies when you tap into the memories of your previous lives.
I know that everyone is saying it is "unbalanced" but on that basis so are most of the Powers. For example, Inhuman Strength gives you a +3 bonus on Might rolls when lifting or breaking things, +1 when using Might in conjunction with grappling (and the ability to inflict a 2-stress hit), +1 to modify skills based on Might, and +2 damage in melee attacks. All for -2 Refresh.
That is at least the equivalent of 3 mortal stunts (-3 Refresh) and might be 4, so is discounted, which (according to the rules) is appropriate as they're based on pre-requisites (typically a High Concept link) and thus can be slightly more potent for their cost.
While acknowledging the "arms race" risk the High Concept links mean it always needs to be justified via an Aspect. I also think the KC costs are far too cheap for such a power so want to break it down and work out an appropriate price. I suspect the cost will be prohibitive unless it is a central part of a characters concept.
What I am proposing is a Power that swaps out a dF for a d6 (averaging +3-4 on a roll) for a particular skill and as a Power it must link in with the character's High Concept (which means linking it to the BCV might be difficult as "supernatural" skill is not something particularly associated with the BC, unlike mind control, strength, toughness etc. Skill via experience is better done via high skill levels).
Now, the problem with giving this a cost is that if used with a weapons skill it is effectively worth "more" than if applied to another skill as stunts only give +1 to an attack under a specific circumstance. Assuming an "average" roll of +3-4 (admittedly it can vary between rolls), then that would be worth 3/4 stunts if only applied to a single use (e.g. attacks) - that could perhaps be discounted due to the pre-requisite cost (High Concept); so -2 Refresh to replace a dF with a D6 for a single trapping (in the same way that Inhuman Might is downgraded by 1 to 2 points due to its pre-req). Extending that to cover an entire skill? Is that an additional -1 or -2 Refresh?
I would say that -4 Refresh might be an appropriate cost for the power, increasing by -4 for each "tier". Thus, being an "extraordinary" swordsman would be -4 refresh before purchasing any other powers or stunts. That is the equivalent of a brawler taking Supernatural Strength with all the bonuses it provides.
Is this about right, or still too cheap?