Some time ago I suddenly realized that Fancy Pants represented everything Rarity tried to find in Blueblood: “Prince Charming” who was “gallant” and “treated” her “like a lady”… indeed, he looks like Rarity’s perfect stallion! I personally like this couple, so I made this picture of them, spending time on a yacht, like in the song from “Sweet and Elite”:)
Just in case I’d like to answer on the main objections against this pairing:
1)“Fancy Pants is married” - it is not confirmed in the show that he is married and his relationship with Fleur Dis Lee is unclear. Although he is often seen with her, Fancy spends much time alone as well (he didn’t take his wife to Wonderbolt Derby and garden party in Canterlot Palace?)
2)“Fancy Pants is too old” - I’m sure that he is older than Rarity, but it doesn’t mean that he is too old for her. I personally don’t think that their age difference is insuperable. Especially if you compare it to the shippings of ponies with Celestia, Luna or Discord…