I just had a major issue beacuse the RADIUS certificate of the NAC/IAM appliance did expire. This caused a big problem because of IEEE 802.1X Authentication was used. The problem was quickly resolved but it could have been avoided if an alarm would have been present.
Best scenario for future releases: If the RADIUS (or any NAC certificate) is about to expire (e.g. in 1 or 2 months) a warning is presented. And in the last days an alarm is caused.
I hope this idea will be realized to avoid major .1X problems :)