Well, the problem is the exe name, its renamed so it can coexist with the original exe. And the cRPG launcher will not use the original named exe, what probably means that if you rename the old warband to the original name, the launcher will not use it, because of the name.
And steam will not launch with the wrong exe name, not recording time played, achievements, and using the overlay.
Yes you can add as a non steam game and use the overlay, but really the overlay is the least important thing to me.
I GOTTA TRACK MY GAME TIME!