The biggest hole that we are seeing with fully managed phone profiles is that SMS messages cannot be backed up due to our InTune policy to block adding google accounts. If we could control which Google accounts could be added (say only ones using our email domain) that would be great, but since we can't, we had to disable this.
Many of our external Trades only text. They don't want to install apps, they don't want to change anything and just use SMS. When we do this on fully managed, we have no where to backup these SMS messages and they are used for work purposes. If their phone breaks where Smart Switch or other apps can't be used, we want these to be backed up.
Even better yet would be to have some sort of SMS ability in O365 so that we could push that app to the work profile, have the data backed up to the Employee's O365 account.
What do businesses do when they need SMS capabilities for work without having to force every recipient to download an app (like What's App, Signal, Teams)?