Would like a full page calendar view that would allow users to specify an estimate of how long a task would take and then drag and drop tasks into the calendar (which would then sync back to Outlook Calendar and block that time out in my diary).

I think this would be a really good addition to your product to provide customers with a much more visual planning tool. For an example of other products that do this, maybe take a look at https://ellieplanner.com/. This is more of a task management app and only integrates with Google Calendar but you will see the sort of thing I mean. You can see your calendar alongside your tasks and then plan them in.

I think you could have a view that shows calendars in week views as well, so you could schedule across the week.

I would like to add time range to my action items and my action item to show up in my google calendar as a task for that date and time.