If you do the CPL exams, but then "move onto air taxi type work etc..." where you will need an IR, you will then have to sit the IR exams before you can do the IR training. There is an overlap between the CPL exams and the IR exams, so you will be duplicating effort.
What's more, having obtained your CPL and your IR, if you then acquire 500 multi-crew hours you may like to upgrade to an ATPL. But you will now need to sit the ATPL exams, which will require re-sitting all of the exams which you've already done (either for the CPL or the IR exams).
Mad, huh? Which is why, if there's any chance that you're going to want an IR in the future, the best advice is to do the ATPL exams from the start.
The disadvantage of doing the ATPL exams from the start is that you must then get your IR within 3 years of the end of the month of your final exam pass, otherwise the exams lapse and you have to do them again. Once you have the IR, you must not let it lapse by more than 7 years, otherwise the exams lapse and you have to do them all over again.
FFF
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