If your medical is revoked then it is revoked........licence invalid. Full Stop.
Several cases similar over the years. One case of the big "D" caught one guy just a few days before annual LCC, which then expired; complete re-validation from scratch was needed.....board, practical..everything. Don't book a medical until after LCE would seem to be reasonable advice [this assumes that the 90-day rule is not a factor].
Another case involved a return-to-work after illness just 24 hours [one day]after expiry of 90 day period........complete validation required again. Same controller re-validates and unfortunately goes sick again. On return to work is then promoted to post where validation is not required. This is not as gross as it sounds......in NATS if you lose your licence wholly/partly/temporarily you will be given a non-operational job which then places you in an ideal position for promotion. The worst career move you can make in NATS is to never go sick and just get on with your job keeping your nose clean.
A useful dodge for controllers on maternity leave is to pop in to work for a few hours part way through the absence to keep the ticket warm, and thereby circumventing the draconian rules with a little common sense application.