Flexible Privacy Option


I hope I selected the correct category for this.
I definitely like the “private” option on twitter, so thank you; however, sometimes, I need to make a reply to someone, while my page is set on the “private” option.
Would it be possible to have that capability to stay private, yet have an option to select “private” or “public” for each individual tweets?
I know that Facebook and Tumblr has that option, and it’s very convenient.
Also for example, if we only need one tweet to be visible to the public, can we have the tweet to only show up on the person I’m tweeting to, and not on my own timeline? That will be really cool.
Thank you for considering.