As far as I know DDNS = Dynamic DNS and is used for assigning an address for people on hosting accounts where their IP may not be static. So someone with an ADSL account at home could host a site on their home network and the DNS would resolve. Am I understanding this correctly?
If my understanding is correct DDNS has nothing to do with 301 redirects. You're comparing apples and oranges.
Could you explain a bit more about how you intend to use DDNS in place of 301 Redirects?