To get a fATPL, you need a CPL, an IR and to have completed a Multi-Crew Cooperation course.
The ATPL exams are just an amalgamation of the CPL and IR exams, where candidates can cut down on the amount of duplicated study and exams.
If you choose to do a CPL separately, then 15 years later do an IR and MCCC, you could still apply for an ATPL.
If you've got your CPL but not got your IR by the time your exam credit expires, then you should just be able to do the IR exams at a later stage.
Once your CPL is awarded, that is it. It's yours.
The ATPL exams just prove that you've done all the ground school required for a CPL and an IR.
I'm not sure about the FI rating though... do you just need a CPL, or do you need to have completed the exams within a given time...?
Of course, there is no mention of the FI rating in the FCL section of the SRG website...
