Parson I really don't have a clue.
The cynical Scotsman in me thinks its all part of a cunning plan to get all airline training through MPL.
The other side of me says its just clueless people making rules up with no thought about how it would work in real life.
The only way I can see to do it is to get 1000 plus PPL instructing get a twin MEP job surveying or the like then after a couple of years doing that while keeping your FI up get your CRI MEP and IRI. Then find somewhere that will let you do CPL and MEP and when you haven't bent anything for a year they will let you do IR 's as well.
I can't see most typical FI's being able to do the MEP IRI leap. You may get a few that will go to SEP CPL training but the next jump is almost impossible unless the school lets them do ferry trips etc to get the hours up for the CRI.
Unless you in the system or step out to a commercial job your pretty well stuffed.