My suggestion would be a bit of long term bondage, with him absent at least part of it.

That is, on a weekend have him tie you up and blindfold you, leave you like that for the night...you could even leave windows/doors open/unlocked...at least one time during the night, he comes back to have his way with you, but can't speak...leaves when he's done, returns in the morning to unlock you. it's not perfect, but at least there's the believable sense of "who could it be".

Heh...I could probably give him a couple tips as well for small touches, but relaying them through you would probably lose some of the surprise.