I am just wondering why you are even considering taking the CB-IR theory as you are already studying for the ATPL exams?
As then I'll have my rating in a few months and can use it on a 20 hours total flight time round trip for my job in the spring instead of flying airlines, while I won't have the ATPL in more than one year yet due to my current work schedule. Yes, I would do some extra theory but I would get most of it back when studying the ATPL later. But I asked these questions to decide so your input is valuable, I am getting a lot of insight, at least I understand that the CB-IR _rating_ (not theory) would be okay for commercial flying if I get the CPL later.