Ability to set Task durations, and Calendar suggests tasks based on availability and duration
Ability to set an estimated duration for a Task (perhaps with ability to set a default time and quickly change), and then have the Calendar suggest Tasks you could work on when it sees you have the appropriate amount of time open in your calendar.
Charlie Sinclair commented
Taskline Add-In automatically schedules tasks to free time slots in your Outlook calendar:.
Christina Sanchez commented
Display overdue tasks in red text when previewing tasks with Outlook Calendar to be consistent with overdue tasks displaying as red text when previewing tasks in the right pane next to emails. Red text is quicker to recognize how many of your tasks are overdue and which tasks require your attention first. This is very important when previewing how much time you have that day to actually complete those tasks.