Nice post, really nicely writen. You have answered to all of my questions. As you said there hasn't been a proof of which theory is correct. I am also leaning more towards the theory you posted at b). So in that case the best thing to do is to train driving and handling to some point because 1on1 also do not train OD . And then only focus on OD. So, If this theory is correct you wont loose no training speed in driving and handling, you will only get a big boost in OD. That was also what I was reffering in my question. But since this hasn't been proven, we will never know if this is true or not.
Thanks for your post.