Okay, there are several thing that Karu missed while half asleep.
First off, you're only allowed to begin off with one element as a genin. By your own write up, Brine is an advanced element requiring Yin and water. In order to use this, you'd need to start with either Yin or water release.
In regards to the Salt physiology, this is cannot be allowed at all as it clearly can be used in combat whether its the user's intention or not. The moment you are struck with a water technique, the water becomes infused with salt, which is the whole basis of salt release.
While it may not seem like much, this is clearly a combat SC, and thus, cannot be approved.