As cute as the idea by Nunnally side is, I agree that it would not be fair to the dynamics of his character. And people in the fandom really do side with Lelouch more on most things. Me, I used to be annoyed with Suzaku but now that I've seen he's more than just some blindly charging hero, I enjoy him more and appreciate the chance to pit his views against Lelouch's.

I like your options for Suzaku's feelings during the ceremony. I do think that he's pleased at the chance to work more with Britannia since his whole deal is to change them from the inside. He probably appreciates the chance to spend more time with Euphemia as well. But at the same time, he knows how much this will increase Britannia's resentment of him.