What features could be added?

Understanding what features could be added to your equipment is in fact the most important stage in all this process.

...That is why it's going to take a while to put in writing!

Here is a partial list, Based on SONY camcorders:

Enabling inputs Like composite and S-Video: most SONY camcorders come with output terminals that could be used as inputs! This gives your camcorder the ability to record from an external source - for editing or just of-the-air recording!
DV inputs / outputs: It all depends on the model, but usually possible. I don't have to explain how important this feature is! right?
Doubling digital zoom: From x24 to x48 or from x30 to x60!
Enhancing low light sensitivity.
Disabling the annoying drop in picture quality when "steady-shot" is activated at low light levels.
Turning a PAL camcorder to NTSC and visa-versa!
Enabling LP where not available.
Bought you camcorder in Japan? does it "speaks" only Japanese? Tell it to speak English! (or visa-versa)!