For me, I am an engineer who is doing research with UAV technologies. So, yes you don't need one to perform the functions that you are talking about, but eventually this information might be useful. I will probably have to use this information to somehow improve on the fixed wing UAV control systems. So although it is not specifically needed for your application, some people could find it useful, even if they just look at the speeds to see if they match up with other flight data. :-)
It's not technically needed - I have flown in auto without an airspeed sensor. If there is enough stall margin as you say you won't have too many issues, and the APM can rely on ground speed from the GPS. If there is a high-wind, or more complex manoeurvres such as landing then airspeed sensor helps a lot.
so this was the answer i guest?
quote from Micheal Thomas above;
"If there is a high-wind, or more complex manoeurvres such as landing then airspeed sensor helps a lot."