TTWD = This Thing We Do (doubly safe, as an initialism of an already secretive phrase)
raisedkilt:
What do you do when your vanilla spouse says NO to TTWD?
You could try reading WellRed Weekly Volume 1 Article 10, helpfully titled "Getting your vanilla partner to whack your butt" and you might also consider Volume 6 article 3 "The Satisfaction of Self-spanking". The 14 volumes of the Weekly are available under Sites (between Features and Logout) and contain about 160 fascinating articles - hours of browsing fun there.
I sympathise with your big sigh. It's usually inadvisable even to begin thinking about the idea of contemplating trying to advise, but... if it were me, I'd keep trying to find a way to coax your wife into sharing her own best fantasy and take it from there.
I just finished reading "Sex with Shakespeare" by Jillian Keenan. Late on in the book she describes how - after years of frustration - she finally managed to get her husband on board with spanking her the way she wanted. He wasn't stubbornly uncooperative, but, as a vanilla, he just didn't get it and her timidity matched his. Her advice is simply to talk, talk and then talk some more - keep communicating. This may not be helpful to you initially, but if you can find a chink in your wife's refusenik armour, then it probably will become so.