If you do a CPL and an IR you need to do 13 exams for the CPL and 7 for the IR = two courses and 20 exams, and you still will not have the ATPL theory credit which is required if you ever want to fly multi-crew aircraft in excess of 5700kg MAUM. This is why most people take the 14 ATPL exams straight off - they cover the CPL theory for licence issue, the IR theory for IR issue and give you the ATPL theory credit for multi crew aircraft. Granted the syllabus is a bit deeper but it is considerably less hassle and you get the ATPL theory credit which you will need if you ever do change your mind and go for an airline job.