you know that some of these appliances have a fan, but its actually now a draw out of the house type fan. It has a according type filter that just traps grease and other stuff. Never understood the need for a fan if its not vented. They call it a self contained fan unit. Strange.
Anyway, my experience is that when venting, you want as few bends in the hose as possible because debris, grease, and stuff collect in the bend area. Use as big a hose also as possible. Now to your question. They now make those neat exterior roof, or wall hoods that actualy work quite well. you could mount this on the exterior, run your hose, cut your holes, and be done with it. Make sure that the opening on the exterior is high enough, away from branches to keep out the rodents, they love the smell of that grease and what you have just cooked.