It's quite possible to use it that way. You don't just want the bottom half of the throttle stick to be unused and the middle to correspond to zero throttle.
At some points in setup you will have to hold the stick down.
It's as safe as a gun or a car driving down the road. If you forget and don't follow proper procedure, something or someone could get hurt.
To arm it using the typical low throttle and right yaw, you would do exactly that, but if you release the stick after that it will jump to half throttle so you will probably want to be careful with that.
On Revo (not CC3D), Altitude Vario and GPS modes use mid throttle stick to mean "stay at this altitude" and a spring on the throttle actually makes sense for that. These modes aren't available on CC3D which has no baro or GPS flight modes.
If you crash you will have to remember to hold the throttle stick low to keep the motors from spinning.