I'd either do diagonals OR do straight through the middle of the squares ....
But you could also do small curves corner to corner -- but that's a lot of curves! But you can do them in a linear fashion so you aren't having to start and stop any more than straight lines!
Or you could do a larger curvier pattern overall in a thread that blends (say grey) so it doesn't take away from the piecing. But I would do much custom otherwise, because it will get lost!
Beautiful quilt by the way!