Sako,
My advice would be to stay with a simple round tube for your battens. You might find something with two grooves, but it probably won't be optimum in terms of the strength and stiffness you need. In many, many miles of sailing, I've never felt that I needed to take out a panel for repair. It's usually a case of either gluing a patch on a small hole, or taking the whole sail off at intervals for a major overhaul.
On the other hand, I've needed to take out a batten, and then to find or make a replacement for it, far away from where I got the original battens.
Now that we have several ways of sewing sail panels together and making pockets that do not need the whole sail to be laid out on the floor at once; and now that Roger has successfully made his sail with the batten acting as a "hinge pin", I can't see any justification for adding tracks to battens.