You realize that modders can do ANYTHING the official programmers can do once the hardcoded functionality is in. Provided the mods are of high quality you've laready got your expansion.
You know what? You are right. In fact I dare say that modders can do a better job than the original programmers through sheer zeal. But y'know what? people don't like free stuff no matter how much better it is, we'll always have it that way because people are paranoid and automaticaly assume higher price equals higher value. Good examples of this include bottled water and Linux. If this ever changes we're in for a better world but until then corporations have us in their grip.
If anyone reads this I compel them to use
The Gimp rather than
photoshop, It's the taster's choice!