This would be applicable if the OP uses a direct connection for Smart Licensing, aka connect to the cloud SSM directly from the device. If the OP uses an on-prem SSM the change in certificate should not affect the router as such, but the SSM would need to be updated to include the new certificate.
All this said, I would agree with you that it’s better to go for the version that you suggested.
You should look into the process called Device Lead Conversion, DLC in short. This is supposed to handle the conversion of licenses to Smart Licensing. Please note that this is renowned for not working great and that will lead you to have to open a SR with the global licensing support team to get their help on this. They would require that you provided the license UID of the device and the serial number.
After the grace period has ended the router will stop working as a voice gateway as it would not have that feature set available in the licenses.
Well we have just done this conversion on all of our 140 or so ISR4K voice gateways, so I’m sure on this. But your free to not take the advice given.
