IMO, if you're saying that you probably would be specifically denied a license due to the product similarity, proceeding anyway without a license probably isn't going to turn out well for you if Microsoft ever catches wind of it.
I would go with Option 3 to be safe.
I realize you say that you don't care about the patents issue, but that's really the only issue. Even if you were to aquire a 3rd party ribbon control, Microsoft has the patents on it and can come after you for violating them. They've explicitly come out and said that people can use it for non-competing products.
The Office UI license restrictions are for the concept of the ribbon, not just MFC's specific implementation of it. See this page for more information.
I suppose what it really comes down to is whether I'm a direct competitor to MS. Any product can use the ribbon as long as it's not a "competing product", whatever that means.
In the context of my theoretical question, I would certainly be a competitor, and so I'd say it's too risky to use any kind of ribbon.
Of course in real life, whether or not you're a competitor isn't quite so black and white. I'd probably go with Option #2 for any product apart from OpenOffice.
EDIT
I watched this video and here's a quote from the MS lawyer in it:
"The license is not available for applications that have the same primary functionality as the 5 applications that currently have the ribbon in office. That's Word, Excel, Powerpoint, Outlook and Access."
The word primary gives the impression that a product containing a rich-text editor could have a ribbon bar on it, as long as the product's main purpose is different to Word. e.g. a version control system which allowed rich-text comments on checkin, would probably be OK. (I guess)
Even if you are using a Ribbon from a 3rd party control, isn't it the case that you still have to acquire the license to use it in your application?
If you're interested in exploring the third party component route, the article on CodeProject that I link below features a ribbon that looks a lot like Microsoft's and is freely available (though you'd have to credit the author).
A Professional Ribbon you will use (Now with orb!)
I haven't tried it but the article is highly rated (FWTW).
If Microsoft ever decides to come after you, you're dead. Regardless of the merits of the case, you'll be forced to settle just to keep from bleeding to death with lawyers fees. They have much deeper pockets than you do.
And remember that in the U.S. at least, damages for patent infringement are much greater if they can prove you knew about the patent and willfully violated it. Posting in a public forum would be proof enough, I think.