If the vent flaps are controlled by vacuum pods, and there's a vacuum supply line that you could tap into, then it's likely that you could install a switch to manually control the center vent. However, you'll want to tie into a vacuum source that makes sense to tap into. If you tie something into the "always on" vacuum line, then you might have to perform two actions to turn that thing off. For example, if you have the defrost running and the center vent opened (with your custom switch), and you want to switch to footwell only, you'd have to turn the built-in dial to footwell, and you'd have to turn off your custom switch for the center vent. Most people don't like having to do two things to get one result. The nice thing about my mod is that it utilizes a vacuum source that is only on when the appropriate buttons are selected on the ACC. If you are running defrost, the center and footwell pods don't have a vacuum source because they should be closed.