Flavoring A One Year Old Mead - Vanilla

I have a basic mead I made one year ago that has been bulk agin in a carboy. My wife would like a vanilla mead so I thought the about putting two fresh vanilla beans in this mead for a couple weeks or so (to taste) and bottling (or drinking ).

Has anyone ever flavored at this stage? Any pros or cons?

I can't see why not, just don't mix it up to keep that blanket of Co2 in place.
I would split and scrap the beans, just in case you did not know, and depending on the bean they can be pretty strong. I would consider using just one for a week. Then racking / bottling to seal them up.
The problem with vanilla is it is very strong at first, then weakens over time and I usually just use it as support for other spices like nutmeg and cinnamon.
Best of luck,