Interesting. Now that you mention it, I've also tried OpenRa a couple of times and I also just didn't like it because it was so different from the original.
At any rate, yeah, my intent is to clone the existing game as is, and then to potentially have a version with a few tweaks. But this is all a long ways off....
One thing I learned from my Robotron clone is that it's actually very hard to tweak the gameplay of an existing game and have it still be fun and balanced. For example, I thought it would be fun in Robotron to have a shield that the player could activate for a few seconds, but that ended totally unbalancing the rest of the game and making it much too easy. So then I tried to make something else harder to balance it back, and I found it very difficult to get it just right and still be challenging AND FUN. It made me realize that the 'programming' part of the game is VERY different than the actual game design. And the game design is MUCH harder to get right.