I agree with Dave. Please support the MetaWeblog API over SSL. If that's not secure enough for you (and isn't basic auth over SSL good enough?), then implement Atom over SSL. Please don't provide another gratuitous set of APIs. Just extend prior art and have open APIs, please!
From Scripting News: 12/2/2004.:
Dare Obasanjo, who works at Microsoft on the Spaces project, considers blogging APIs. Here's what I would like to see them do. Support the Blogger API with Metaweblog extensions over HTTPS as Dare describes, and then carefully and slowly introduce APIs to cover the other parts of the functionality, with feedback from tools developers as you go. No overarching ocean-boiling, just boring, repetitive, dumb but easy to understand XML-RPC interfaces.