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*shrugs* I'unno, energy manipulation is a weird thing since it's only limited by what you say it's limited by.
And nowadays people will more readily accept you can do something with 'ki' than with 'magic'.

Since apparently the existence of a powerful enough version of the body's bioelectric system that it enables the power of flight, the means to make your body as hard as steel, and the ability to plain blow s**t up is more reasonable then the existence of some outside element that allows the pulling of rabbits out of hats.

But that's just a tangent, my only experience with heavy chakra usage is Tenjou Tenge. And in the manga everyone (with the exclusion of Nagi) had one 'Dragon' ability corresponding to a chakra. Like in Naruto where he's gotta find what sort of elemental ki he has. Then that's your ability/chakra and you hone your techniques according to it.

There are existing Oriental theories for selection of such things or you can just pick one you like.
I mean, Shouyin wasn't born in an Earth month according to the Japanese, but whatever.

So really, I would recommend just going with one chakra and being creative. But if you want all seven or eight or whatever, then just being able to tap into one at a time seems a pretty reasonable idea considering that is what Nagi does, and since if you used 'em all in combination you could do -anything-. I mean, all of them allow for fancy energy punches and sixth sense and stuff, really it's just a matter of picking one you like best and making more specific abilities.

Dunno about the whole tapping into two at once, but if there's a noticable penalty that's koul.

Mayn, you stole the concept from the Chinese anyways, can't say it's specifically yours to begin with.
And only koul people read the Tenjou Tenge manga nowadays, so no one'll call you out.

Except for like, me and Vahn. =D