Well you would fall foul of your license being out of date, to renew you would need a medical and a class/type valid.
After that its just a normal IRE that does it. It also depends on if the IACO is valid at that point in time if you have to do refresher training or not. There might be some rubbish after 5 years that you need to send your license to the CAA again to get them to put it back on.
The theory stays valid but you also have to jump through the hoops on which ever class/type you have. Which very well might mean you have to jump through hoops to get that back then do your test with an IRE unless its a type then a TRE can do both at the same time.
So its a two stage and two sets of rules which you have to comply with.
I don't have a clue what the new rules are going to be.
The changes with EASA are doing away with Staff examiners who I believe are becoming more of a standards inspection team.