I'm still not seeing how this power is any less harmonious than Inhuman Strength - it works differently sure, but Inhuman Strength also makes potential stunts and/or skills obsolete by its very nature.
Eh. It does make one or two possible stunts look weak, but even those stunts are still worth taking sometimes.
More importantly, you don't have to rewrite the rest of the game to make it work. That's what makes it harmonious.
For example, want to be a grappler? Which is better, taking Inhuman Strength and its bonus around grapples or a couple of grapple related stunts that try and do the same thing? Obviously it is Inhuman Strength - it gives you way more bang for your buck.
Nope.
The stunts are often worth taking either alongside of or instead of Strength.
Who is better at breaking things? The character with Might +3, or the character with Inhuman Strength? Mechanically, they are the same, except the power cost Refresh and the skill didn't. Oh, and the power gives a bunch of other benefits...
To be fair, the skill also provides other benefits.
Inhuman (and Supernatural etc.) Strength is a way of getting a high "Might" score without increasing the Might skill. Inhuma Speed gives you a similar bonus to Athletics - it makes you better in some situations without having to put the points into Athletics.
What I am suggesting is a way of getting an effectively high skill, without the skill points. It is just "generic" rather than linked to a set use of a skill.
I don't think the word "just" belongs there. Generic-ness is a big deal.
In canonical Powers, there's a fair bit of attention paid to which bonuses are appropriate where. Mythic Strength gives +12 to lift and break, Mythic Speed only gives +3 to dodge. Because huge lifting/breaking bonuses aren't a problem. Huge dodge bonuses are (sometimes).
There are some places where it's appropriate to hand out massive pluses. There are others where it's not. If you want to hand out massive pluses everywhere, you're gonna have to make some changes.
Which brings me to the bit that you appear to be missing about the link to High Concept - I am not saying it is a "cost" in a mechanical sense. I am saying it is a pre-requisite to take the Power. By making it link to High Concept the Extraordinary skill has to be a core component of your character concept. It is not a power that people will just pick up "because" it is cool, particularly if the refresh cost is costed correctly.
Yeah, but the fact that it's core to your concept shouldn't reduce its Refresh cost.
Firstly, the fact that this Power makes someone the equal of someone with an Epic skill is the point of the Power; the Power is for those that are supernaturally "better". They are different ways of reaching the same point (and the Power is less certain). One is through hard work and discipline (i.e. raising the skill to Epic), the other is through supernatural ability (the Power). Characters with the Power (which is linked to their High Concept) are meant to be supernaturally talented "the best" at what they do. Their innate ability is such that they are the equal of characters that have spent years/decades/centuries mastering their abilities.
I get that. The issue is that skill ratings above Superb are a really big deal. You could stat Mab with a skill cap of 8, no problem. (Some of her Powers would be really tricky, though.)
These Powers completely change that basic assumption.
Secondly, the canon NPC descriptions are, as described in OW, based solely on what had been revealed in the novels up until that point - in fact in a number of places it notes that the descriptions are likely serious underestimations of the character's power. Given that, assuming that the Epic is "the highest skill" is probably underselling those characters. It is simply that those characters are incompletely described. Given that, whether Epic is "the highest skill" is very dependent on the game.
Eh. I run an 18-Refresh game. I've only used one or two NPCs with Epic skills.
High skills are a huge freaking deal. Huuuuge.
Such as? What needs to be fiddled with?
Anything which uses a skill's passive rating, including the mechanics for stress track length and the mechanics for skills modifying each other.
Spellcasting.
Declarations.
A bunch of NPC write-ups.
The supernatural/mortal divide.
The stunt rules in general, and stunts which let you move trappings in particular.
Maybe some difficulty tables, like the Resources cost chart.
Probably some other stuff too.