Personally, I think rocks are great. I've kept more imports than CB, but probably 90 % have tamed down wonderfully FOR ME. With imports, even the tame ones tend to be a bit restless when you try to handle them - meaning that they just don't sit still. You may find that CBs are better in that regard...then again, you may not (mine really weren't, but I sold the CBs by the time they were 6 ft). They do tend to strike toward the face, which is a big no no in my world. They are also, pound for pound, the strongest snakes I have encountered - and I have worked with pi$$y retics, scrubs, and anacondas. Given the strength, and size potential, I would urge you to consider this decision long and hard. Check the legality of owning one in your idea (as Joe said, they are banned/illegal in many areas). Learn as much as you can about them, and if you get one, plan on learning about IT. Rocks can be enjoyable and interesting captives, as long as you take the time to familiarize yourself with their ways. Some people just can't relate to rock pythons...and those people should not own them.
I do kind of see a problem with your statement about by the time it gets to be 16 ft, you'll be ready for it. You should be ready for it before you get it - they grow quickly, and can become problematic by the time they are 5-6 ft. most of the rocks I had, I received because their keepers did not want to/couldn't deal with them anymore (in some cases, they wouldn't even open the cage to clean or feed because they were afraid of it)...many had had the snakes since they were very small. Placement of large constrictors is becoming more and more difficult, so before ANYONE gets one (and this includes boas, burms, retics, anacondas, etc) they should be darned sure they know what they are getting into, and be prepared to deal with their choice.