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there is actually no rational optimum solution
Being able to use the front brake while signalling a right turn, sounds pretty rational to me.
As does improved braking (and shifting) performance: cable routing isn't just an aesthetic consideration.
People manage to swap between road/MTB, Shimano/SRAM/Campag and fixed/freewheel etc without bursting into flames and plenty have motorbikes and cars as well as bikes.
You can teach an old dog new tricks! ;)
Scilly.Suffolk-
Right, but there are also compelling counter-arguments for the front brake being on the right: if you're signalling a right turn you're turning across traffic, and so you may need to stop with one hand off the bars; having your read brake on the left means you're less likely to go over the bars if you mistakenly grab a fistful of brake. There's also the argument that it's better to have the more powerful brake controlled with your dominant hand to help power and modulation.
And you can absolutely learn to use switched brakes, but the paranoid argument is that under stress we often revert back to the first learned behaviour, which might be suboptimal. Like I said, it's an issue on which people can go back and forth forever without getting a result:)
Thrustvector
I appreciate that this is a Holy War issue, and so there is actually no rational optimum solution (though obviously you are Bad and Wrong and the front brake should always be on the right...), but in general changing what you're used to just to improve cable routing is a Bad Idea; if you forget you either lock the rear trying to do an emergency stop, or send yourself over the bars/lose the front when trying to scrub off speed.