Yorkshire Puddings with Fish in Sauce
This has made me so hungry I came back down to write!
1:  Yes!  But I would not use roast drippings or suet as shortening for fear of overwhelming the fish with beef.  Anything else.  Duck fat would be lovely.  Lard or vegetable shortening or butter ok.  It might not be as stiff with butter.
2:  Have sauce added by diner on top right before eating or it will sog out the pudding.
3:  What deserves to be in with the fish?  Leek or carrot or parsley all very precious and would be visually spectacular.  But thinking @bob1 deconstructed fish and chips... what do you put on fish and chips?  Vinegar.  What wont soak the pudding but is vinegary and has some veg crunch.  A pickle!  A pickle spear in there with the fish would be perfect!
I was thinking also some of those crunchy premade onions like Frenchs makes for salad and hot dish but that is my belly talking.  You could have those on the side for the Americans to sprinkle on.