It is 6 of one, half a dozen of the other.
Since you're in JAA/EASA land, keep an eye on the time line for the ATPL exams lapsing and finishing your IR.
So, the idea of doing a FI isn't a bad one, so long as there's a chance of some work at the end of it. If there is (and it's genuine work) then it will keep your hand in & begin to get some hours up. If you want to improve your chances of a job after wards, be the most diligent and conscientious student you can be.
If you're cash strapped &/or no real chance of gaining any hours post FI, then put every thing on hold for 9-15 or so months and then hit the IR (Assuming you have "time" in hand for your exams)