I can confirm this too. My rouge is a custom character with the highest mechanics in the party. I tried to dismiss and rehire him, but he is still unable to pick locks.
Yes, creating more companions sounds like a good thing, but only if they integrate with the story, the already existing companions, etc. seamlessly. In that case, I think they would be a great addition.
In fact, I have already increased my pledge. But I probably would have without the new streatch goals anyway...