I think that anything that takes the focus from fighting to gain exp is good.
Why not have it so when you sucessfully manage a skill such as a healing nano, (e.g. you hit the top health given) you get some experience, or when you manage to hit with a pistol at the max of its damage, or you get a critical hit.
That way you actually recieve experience from using all of your skills.
I like the idea of Exploring, however I don't think it should give exp, perhaps it should allow your navigation skill to go up, that way after you've gone around exploring for a while your navigation will have improved.