Yeah, probably. Except it might just be a lot more work to learn, then write, the program than to just do the work. Of course, if he then needs to change something... yeah, learning a scripting program would be helpful!
Nah, changing the amount of asteroids in the planet files takes about 5 seconds, renaming the files and adding it to the definition file takes much more time then that.

Planets that are pre-inhabited by pirates and require bombardment, planets with tougher militia forces,
Actually you can set this stuff in the .galaxy file.
And of course stuff that might not work, making NEW planet types like Jungle, Barren, Oceanic. And converting a new resource asteroid into a moon model; and Nebulas with NEW abilities. Not to mention whatever addons the release version requires me to rethink, like extra or new planetary abilities, like the ion storm.
Making new planet types is as easy as making a good looking mesh with corresponding textures. So... yeah.. well...

If you're still at this after the game's released (not much sense in trying something like this before release) I would volunteer to help. So don't worry about your sanity.