Of course that's a lot of other way to do this. As melanie said It depend of your knowledge on video, the time you have to spend on (developpement, Character database,font, special character, and more.....)... thats for sure. LM1881 is one of those cheap IC i use in the past and it's working really well + you can find it almost anywhere for a few $.

You can mix your video signal with high freq op amp and it give to you the benefit to adjust the gain of each signal depending if it's neat or not at the end. But a few cents transistor+load of resistor may do the job too.

if you want to see how easy vdo can be done look this article i found with a few second Google search
http://www.rickard.gunee.com/project.../pic/howto.php

good luck