Now, I know right now no one is flying hundreds of miles away with their UAVs, but I envision the day in which UAVs are limited not by the plane's capability to traverse that distance, but the owners willingness. So why not think to how we can easily improve our current systems to someday do things we may not have thought possible.

That's my fancy way of saying I have an idea that has little practical value, but I want it to sound at least somewhat meaningful :P .

Why not account for the curvature of the earth, the antenna won't be off one degree every hundred miles?

dlat = lat2 - lat1
dlon = lon2 - lon1
a = (sin(dlat/2))^2+cos(lat1)*cos(lat2)*(sin(dlon/2))^2
b = 2*atan2(sqrt(a),sqrt(1-a))
c = 6373*b
d = altitude*(whatever you need to multiply it by to convert to km)
e = tan(d/c)
f = (360*c)/40041.47
g = (180-f)/2
h = 90-g
finaldegrees = e-h