Simple feature that I think would be incerdibly valuable in Outlook: let a
person specify how many hours they need each day to perform miscellaneous
tasks, and manage their free/busy status with this in mind.

Apart from my many scheduled meetings, I need (say) three hours per day of
non-meeting time in order to get my work done.  A key point though, is that I
don't care which three hours it is;  I just need three hours.  I'd like to
configure Outlook to know I want three hours kept free, and then when someone
tries to schedule a meeting with me that would drop me below my desired three
hours of unscheduled time, I'd like Outlook to show me as busy, both to the
meeting organizer and myself.  

The alternative approach of blocking a few hours in each day is pretty
flawed:  if I block (say) 2pm - 5pm every day, that incorrectly tells people
I'm unavailable during those hours, and if someone can only meet with me
during those hours, then we fail to connect, even if my who morning is open,
and I could therefore easily do my miscellaneous tasks then.  However, under
my suggestion of essentially an automatically floating three hours of blocked
time, Outlook would let a 3pm meeting get scheduled, as long as it saw I had
three hours still free somewhere else in the day.

For miscellanous tasks that a person does by themself, I think it's much
more normal and natural for a person to think in terms of "I need X hours a
day for miscellaneous tasks" rather than "I must do my miscellaneous tasks
between the hours of 2pm and 5pm".  Of course if there are miscellaneous
tasks that really need to happen at a certain time (such as a Los Angeles
person calling their London office during the few hours when business hours
overlap), then normal Outlook appointments work just fine for that.