Why is the president so important anyway? Its not like they aren't replaceable. The people who are more important are the generals and other people with the old knowledge that goes back decades. Attacking the president hurts the country's pride and sense of security, but it doesn't hurt the country in a material way.
Its almost like the president is a decoy or distraction to attract the attention of attackers so that the people with value are off the radar and better protected.
Also, any RC aircraft could hold a mortar round that could be released with a servo lever. That is very low tech by today's standards and would be a terrible attack, and would probably work.
A lot of these little ideas might work, but terrorists usually go for the big attacks, not this little toy stuff.
Also, I hope nothing like this happens in the near future. If it does, everyone in this thread will probably be visited by tall men wearing black trench coats and hats.