Well, I dont really want to recommend that you start kit-bashing on your second model rocket. If you want to build the Alpha more-or-less to plan, you can attach a parachute on the days you want to fly that way, or use a streamer, or use nothing (and try the break-up style of recovery). That having been said, the Alpha III is an excellent kit to buy in bulk (watch on ebay and RocketryOnline) to build more Alphas, or to have on hand for a ready supply of parts for new projects.
When you build the Alpha check the instructions to see if it says to add nose ballast. While a little extra stability is always nice to have, this design has been around since dirt was invented, has already been flown once or twice, and has proven its stability and performance. I would be surprised if you really needed to add ballast.
If you want to use a streamer you can make one from just about anything. You can use the cheapo party streamer colored tissue (at your local party store, or party supplies section of W-mart), but this stuff tears easily and will probably have to be replaced after a few flights (and if it gets wet, you have a BIG mess, stains on your hands, pulped/disintegrating tissue, etc). You can use a strip of plain paper (like copy machine paper); this form of paper will hold folds so you can fold up the strip accordion-like to increase the drag, but this paper will also tear easily and need replacement often. You can get an aluminized mylar space blanket (at your local outdoors store) and cut it into strips; this stuff is highly visible at altitude and is quite durable. I think you can also purchase mylar streamer material by the roll from Totally Tubular as well as other model rocketry vendors.
If you want to add some extra shock cord, or add a length of high-quality string (like kite string) between the existing shock cord and the nose cone, yes you will make a small change in the c.g. (Are you by any chance an engineer?) But the difference will be negligible; again I would not expect that ballast would be needed.
Break-up recovery works fine in small rockets, and was my favorite system for altitude competition. If you make the body tube break just in front of the motor mount, then most of the BT can be permanently glued to the NC. This allows you to seal, fill, and polish that joint until it disappears (here I am assuming that the NC itself has a polished-smooth finish) so that airflow remains smooth, laminar, and low-drag way past the NC and most of the way down the length of the BT. For sport flying, break-up recovery is just another way to go. The Alpha is easily adapted to break-up recovery because you can simply glue the NC into the front of the BT, and NOT glue the BT to the joint on the front of the plastic motor mount. At ejection, the rocket comes apart very easily at that joint (in fact, when building this rocket with kids in beginning rocketry classes, I have seen lots of em come apart at this joint even when they have been glued there to stay together). The only thing you have to worry about is finding a good spot inside the front of the motor mount/fin unit to make a solid shock cord attachment (a bent paper clip epoxied to the inside makes a good strong wire loop to tie onto).
Several examples of break-up recovery can be found on JimZs website:
https://www.dars.org/jimz/rp00.htm
after you get to this site, scroll to the bottom and click DOM at the bottom left (Design Of the Month)
Check out the files for Sky Bird II (#2 on list) and Mitosis (#40). Both of these are great examples of break-up. (If you ever crash your Alpha and have a left-over NC, I think that is the same NC shape called for to build the Mitosis.)
Another recovery setup that is very similar is tumble recovery. The motor shifts position when the ejection charge goes off, moving the weight of the dead motor aft (but being retained) and causing the rocket to be unstable. It tumbles down, returning much more quickly than parachutes or streamers would. Go back to JimZ, scroll down to the oval-shaped Estes emblem, and look on the list of old kits for the Scout (K-1). That is a classic early Estes design, and easy to make a kit-bash or upscale. Other examples of tumble recovery include the Sprite (K-15), and the Orange Bullet (#3 over on the D.O.M. list).
But I don't want my new rocket to crash, either. I wasn't certain if additional shock cord would change the cg enough to worry about, since the overall weight of the rocket is so low.
