Sugar is used in a brine to cut the harshness of salt. You can cut it, but like Rexter said, the bacon might seem salty.
If you want to try Stevia, I would recommend experimenting with a small batch first.
If you do, I'd use the stevia extract liquid NOT the powder. Stevia in powder form would need to be made into a tea first, because the powder does NOT dissolve. It remains a suspension, so it cannot move through the cell walls of the bacon.
I'd also use it VERY sparingly! Stevia is very potent, and it'd be easy to use too much. That would impart a bitter metallic taste to your bacon, which, in turn, could compound the harshness of the salt.
That's my 2ยข.