Since you have a manual mode for the gates, you can prob keep them dumb and rely on hass, because theres an escape hatch. For the extractor youre right it probably needs to keep a certain amount of internal logic and be controllable by mqtt. Rather than making it fully dumb could prob use mqtt to change its current config and ‘hit the buttons’ ie change timers and hit start/stop automatically etc.
Might be value in the extractor being able to tell if the gate system has gone into manual mode? Ie like one of the much older plans about having a signal line go high.