Is there a way to set a "minimum brightness level" on IOS10??

You can try calibrating it. You can walk into a dark place and disable auto brightness, then set it to where you would like it to be when it's dark, and then re-enable auto brightness. It should now work off of that setting as the one being for darkness, meaning in lighter contritions it would be higher than that.

 

As above it's better to set the dark environment to your preference. The phone will ramp up without an issue in direct sunlight

 

Don't you just manually move the slider when auto brightness is on and the slider will never go below where you set it, just higher than where you set it? No matter how bright it is where you are when you set it?

 

Auto off in dark room set to what you want then auto on