Send an email message based on a template not working in new Outlook

We're just rolling out new Outlook, and our staff have pointed out that new Outlook doesn't allow them to use email templates (as per this guidance - to open from template). The email templates they have saved include attachments and are used by a team of people.

If we select the template file to open with new Outlook we get an error "this action isn't supported yet" and a suggestion to use old Outlook.

I have looked at "My Templates" as I use this in Outlook web, but it doesn't allow attachments, and historically it hasn't liked "long" emails, so it;s really only ever been good for short and sweet responses.

Using email files as templates is a key requirement for some of our services, so I'd just like to know if the functionality will be transferred to new Outlook in due course, or whether we need to find alternatives. 

If anyone has any suggestions about alternatives (which allow us to include attachments and save the file where it can be used by a team of people, I'd be happy to receive ideas.