a picture might help.

Some of the GE Monogram ovens have open door broiling - one of their best features IMO. It allows the top of the food to be seared without cooking the whole dish. I don't think there are any true vented ovens on the market anymore. Old Thermadors were vented outdoors just like dryers - you could cook in them, even use the self-clean function, without cooking odors or excessive heat filling your kitchen.

When we remodeled in 1983 our contractor installed one like you described. It was a Broan. I don't know if they still make them but when we replaced our wall ovens 5 years ago we kept the exhaust fan even though our new ovens broil with the door closed. We figured when we accidentally burned the garlic bread it would help to remove the burnt smell.

As long as you can vent it pretty easily and insulate duct and roof properly this sounds like a good idea. I very reluctantly parted with my old ceiling vent fan from old kitchen during remodel--it was no longer in a good place and it was badly installed to merely vent into attic. Although we had a hood over range we often used that ceiling fan (from 1954) when we burned toast, baked salmon, made pancakes. In our house, all the smells went up the split level stairs to living room where they took up residence for days unless we captured them quickly. Am delighted to say that the kitchen addition with the BroanAllureIII hood has prevented this smell track and I don't miss the old vent, but this is sheer luck. Go for it! I've always wondered about venting a built-in oven.