I just wanted to provide an update to this question in case anyone still stumbles across it. Since this was asked, we introduced some new features around resizing. In addition to the existing "flexible" resizing option, we now offer permanent resizing which allows you to resize your disk space as well as CPU and RAM. This makes the old snapshot and redeploy method of resizing unnecessary, and as you are not destroying your Droplet you don't run the risk of losing your IP address.
For more info, check out this article: