Im in the same boat, except for the bigger cock aspect (or the stretching out part).
I just want to see her with two cocks. one in her pussy while she works the other in her mouth.
Ive floated the idea and she knows its a fantasy of mine but so far zero luck.
Try this though....When fucking her or eating her out, say that another man walked into the room
and he now has his cock out. Tell her you want her to suck it good and put your finger in her mouth.
If she responds like my wife did, she will go to town on it.
Tell her to lick it....suck it....bite it, all the while your cock is inside her.
Tell her how much he apprciates a woman like her. Tell her to listen to him moan
and moan with each mouth movement she makes on your finger.
At some point tell her he is going to cum....tell her to suck it all down and
she how she responds on your finger.
She will feel excited and imho I think its a nice baby step toward actually doing it.
In her mind she is picturing it.
Be prepared...One time she asked me who I had in mind? For some reason I never thought this far ahead.
I told her that I didnt know and that I hadnt really thought of that. In my mind it was a stranger.
So there we were stuck. The conversation petered out (pun intended).
So be prepared to have a few folks whom would make good candidates in your mind.
Anyways....thats where I am at.
I put together a list of questions I am going to ask her the next time I get her really tipsey (yes alcohol helps with her).
lmk if you want to see them.
Also interested in successful conclusions for fellas who wanted their wives taking two cocks at once.