Yes.
You could take a GPS module, barometer sensor, and compass, attach these to a PIC, and program it to send the servo commands to the board to fly a course.
However by the time you have written the code, even if you are good, expect to have spent several hundred hours programming. You might as well just use something like an Ardupilot, cheaper than making the custom board, and a lot less work.
Unless you add sensors like this, how is the PIC going to know what to send?. On the ground with a simple 2 axis robot, you could try sending commands like 'forward for 5 seconds', 'right for five seconds', etc., but even without the complexities of wind etc., this will never give really repeatable results....
'PIC' covers a range of processors from very minor devices commonly built into things like ID cards (the sky card for example is PIC based), through things like RF tags, up to quite complex processors used in many things like nav systems. Obviously any processor task can potentially be done with a combination of these, but this will not be a cheaper solution than buying a radio. I'd estimate something like 50* the price of quite a good radio to do anything even remotely 'worthwhile'.....
Best Wishes
