You would definitely leak the smell throughout the entirety of the dwelling if you exhaust into the interior of the wall. Also, take Zagons advice and don't use an intake fan if you could simply have passive intake holes 4x (not 2x) the square inch area of the exhaust opening. For example, a 10" can fan needs a 14" duct at the outlet (at least, preferably 16" if there is a bend in the trunk) to emit 800 cfm. If you thought you could match a 4",6",8", 10" (any diameter) fan with the same size duct you would cut the max cfm by approximately 55-60%. If there's an elbow in the run, you'll be down to 20-25% of the max cfm the exhaust fan could put out.
The theory that one could use (for example) a 6" fan for intake (fresh air supply) and a 10" fan for exhaust is a fatal error. Here's why: a 10" can fan (800 cfm) sucking through a CanFilter 150 and pushing air through a duct silencer and 10-15 feet of straight horizontal 10" flex duct will only expel 350 cfm (I know this as fact because I have 3 of these exhaust lines set-up identically the same side-by-side and I used a velocity meter at the outlet vents and they all release at approximately 350 cfm). If I had a 6" fan pulling air in with no duct connected on either side (typical intake fan set up) I would be taking in more fresh air than I could release because a 6" Can Fan is rated higher than 350 cfm.
It is only in a rare and exceptional case that you would need an intake fan. When you have a very small opening that fresh air can be taken from and it does not equal 4x the area of the exhaust outlet. You would then need an air velocity meter to be certain that you have a negative air pressure because you don't want to leak odors or heat to the immediate surroundings.