This is more of a post-let than a detailed post, but it was an idea that occurred to me and I wanted to get it out there for anyone who might benefit from it or do something interesting with it (which, by the way, is carte blanche for you to do so, if you feel so motivated).
In Fate Accelerated Edition, characters use different Approaches to perform actions, choosing from Careful, Flashy, Forceful, etc. (or whatever other names the Approaches are given).
One classic element of fictional conflicts is encouraging, forcing, or tricking an opponent or rival into using an Approach that puts them at a disadvantage: get a normally careful foe angry enough to attack with abandon, make a somewhat dim-witted rival overestimate his own cleverness, put a forceful, flashy character in a situation where being sneaky and subtle is called for (or vice versa).
This is essentially Creating an Advantage except, rather than sussing out or creating an aspect, you’re shifting the conflict to a different approach. So, on a tie or success, you get a sense of the opponent’s weakest approach and get to shift the conflict there for one exchange. If you succeed with style, you keep it there for two exchanges and, at the GM’s option, can spend a fate point to keep it there for an additional exchange.
Example: Two sword-fighters are facing-off, and it quickly becomes clear they’re evenly matched in the Quick and Flashy department, so one tries to taunt her opponent with a Flashy maneuver to get him angry enough to try a Forceful attack. On a tie or success, she goads her foe into taking a Forceful approach for the next exchange, perhaps giving her an opening for a Quick attack. If she succeeds with style, her foe is so unhinged, he goes Forceful for the next two exchanges at least.
Addendum: Why is this any better than just creating an advantage or getting a bonus? Apart from the flavor of it, shifting approaches can have a more variable bonus (depending on the spread between the subject’s best and worst approaches applicable to the situation) plus it can potentially deny the target access to stunts based on a particular approach: If your foe’s best stunt is based on being Flashy, for example, and you force him into a situation where he has to be Sneaky, then that stunt is likely off the table for the moment, giving you an added advantage.
While I agree with your Addendum, this will actually give a +3 ‘bonus’ normally (assuming the standard Approach spread). It might be a little overpowered. A possible alteration could be that the ‘advantage’ can make it so the character placing the advantage has to choose the new Approach semi-randomly, making the ‘bonus’ be anywhere between +1 and +3 (thus averaging out to a +2).
Or maybe a stunt like Incite Rage will always cause anyone they use it on to use the Forceful Approach. This way, you can’t necessarily choose the worst.
Possibly, you could bring compels into this…
Or this could simply force the target out of the preferred approach for however many exchanges, forcing them to use another Approach instead, which is still an advantage for the wielder.