If I ever wanted to add an IR in the future, I could do the IR theory separate when needed
Yes, you could.
If you then used your IR to get yourself an airline job, you would very soon find yourself with 500 hours of multi-pilot time, and all the other requirements for applying for an ATPL. But unfortunately, you wouldn't be able to apply for the ATPL because you wouldn't have done the ATPL exams......
FFF
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