Addendum to what follows: I'm not sure I'd allow this in a game I was running; while this example isn't broken, one could easily use the same method to construct a ritual that *is* totally overpowered; it sets a bad precedent. (No, I won't stat out why I think it's a bad precedent. Suffice to say that free use of weapon:10+ for a scene is not something I want to have any part of, even if it's costing the caster some serious consequence slots.)
However, if your GM is willing to let you, this is how I'd go about making (and using) such a ritual.
Fist-Focused Chi:
2 shifts for a power 2 attack
4 shifts to upgrade duration from "a few moments" to "15 minutes" (See the time chart in the reference section at the back of the book).
This assumes that 15 minutes is about one scene; I must admit I find it a bit odd that the time chart is mostly in real time units, while everything else is exchange / scene based.
Now, how to cast this. As per page 261, "about a minute" is the smallest amount of time you can get away with for preparing a ritual, even if the actual casting part only takes an exchange or three. However, since this particular ritual is well over your lore skill, you're going to have to cut some corners if you need to actually toss it off that quickly.
Probably your best option for high-speed casting would be spending a fate point to invoke your high concept, and accepting a minor consequence. (For example, a minor mental consequence of "Too focused" that could be compelled to make you miss details or speak in one word sentences.)
If you've got a bit more time ("a mini-scene", which I'd interpret as maybe five to ten minutes), you could replace one of those prices with a skill check to apply an appropriate aspect - probably fists, here, and an aspect relating to various warm-up exercises / katas. You'd still need to pay either a fate point or a minor consequence, but could get away with just one of 'em.
If you've somehow got enough time beforehand for two mini-scenes, you could try to make a second skill check - perhaps discipline for a "focused mind" aspect - and then get your effect with neither fate point nor consequence.
If you want to cast this at the beginning of every day, I'd allow that as just something you do... but it would only be of any use if you get into a fight within 15 minutes of leaving your home; not exactly the most useful option.
And if you want a version that lasts all day, that's another five steps up the time chart... hm... Well, four steps up is "an afternoon", which is listed as more than "a few hours"... Let's assume that time span is good enough to run from a bit after dawn until dusk; that should be sufficient. That'd be a complexity 10 ritual; you could spend a fate point, take a minor consequence, and apply both of the skill checks listed above, taking maybe a bit less than half an hour to get ready for a day you know will be full of combat.
Of course, spending a fate point a day isn't likely to be sustainable, so this is something you'd use only when you were sure you'd need it.
You might also want to look into getting a focus item for your rituals; see page 278. Two item slots could give you an item that gives +2 lore for purposes of ritual preparation; that'd cut down the prices listed above by a substantial margin, effectively replacing a single skill check, fate point, or minor consequence.
(Edit) Looking over the duration rules, it seems that a ritual built like this should only give you *one* free weapon:2 attack, sometime within the next fifteen minutes. I'm guessing Wordmaker's two shifts per level of weapon might be a bit more balanced for something that allows multiple attacks - in other words, instead of making a single attack, you're "conjuring" up an actual "weapon". That'd effectively add two to the complexity of the above listed rituals, which neatly cancels with the addition of a ritual focus item. Oh, well.(/Edit)