A few things....

1. an option to automatically export all tickets to calendar
2. an option to export ticket to calendar when creating a ticket.
3. to have client name showing instead/or with ticket number
4. There are bugs in saving default 365 address in admin section.

calendar and email integration would be great! Also it would be nice if we could share and save files from our Atera
to our office365

https://www.cyberdrain.com/automating-with-powershell-a-much-better-partner-portal/

Intergrate cyberdrain into Atera for O365 management.

Give the option to import users from the specific subdomains.
Allow users/admn/techs to log in with their O365/AAD account using SSO.

Automated billing for licenses and license info

https://github.com/KelvinTegelaar/CIPP

Sponsor and integrate with this - ideas such as quick offboarding/onboarding/alerts

Add license overview and link to product assigned to o365 for license validation

At synced contact level add ability to:

assign/change license,
reset password,
see mailbox size
last login date/time

If you were to do it:

a) Do not require global admin on the tenant (try avoid any admin role if at all possible)

b) One of the most useful would be importing a license count so we can match it up to a contract in Atera and then invoice for the licences, that would probably be the most useful thing I could see for Atera and O365 integration.

As we have less and less clients with servers to monitor it would be great if we could now monitor events in 365 - such as suspicious logins, mailboxes hitting their limits.

Monitoring of the 365 Azure logins to identify failed logins and out of country logins.

My last comment vanished so I'll post it again.

Put this into atera but obviously update it.
https://github.com/bwya77/O365-Admin-Center

You should speak to the guy who made this he's really nice and I'm sure you could work with him to integrate and update it.
I'd post money to pay him again if you add this as he deserves paying like we did many years ago when he used to sell it before open sourcing it.

integration to mark mail as create ticket from outlook to atera would be very helpful. We can show you how this works in another CRM system we use, if that is the case. Many technicians get mails directly from customers even if they know they are suppose to send to a support mail address. Today If we forward a mail to Atera, we need to go into Atera again and reassign to correct customer.

This is really a two seperate items.
Office 365 tenant integration to our customers through our Microsoft Partner connection.
Office 365 integration to our internal Office 365.

Adding date(s) to an existing ticket, not just when creating a new ticket.

+1 for sync'ing users from O365 into a customer as contacts. Managing contacts manually is a PITA.

For all data in the helpdesk system to be able to switched / turned on at choice to be stored in our tenant

Powerapps would be great !

agree with all suggestions in comments. Ideal integration is not management of Office (as is the case with Webroot, or some of the other 3rd party integrations) but actual USE of the 365 environment (as available)

It would be nice to connect a calendar from Microsoft 365 to use for scheduling, technician availability, appointments, client visits, etc, could this be done?

Knowledge base articles that are specific to customers' M365 deployment that are in Atera, be made available under help sections of their MS Tenant.
Similar to how CoreView does it.