I personally had a downdraft and my main concern was that it pulled the flame back when it was running - although you wouldn't have this issue with an induction. Also, since it sits up to the back of the cooktop, you cannot put oversized pans on it as it will knock into the downdraft. Lastly, if you use tall pots in the back it will block the air flow for the items cooking in the front. I would have to say that I would not put one in again if I could avoid it. And if he's a chef, I don't think he's going to like it either.

It really sounds like you need a more powerful dedicated exhaust fan for the type of cooking you do. It's true that microwave units have their limitations. If you already have the ducting to the outside, look into the possibility of getting an external fan assembly that is installed outside. I would highly recommend external mounted units over inline anyways, because it's quieter and probably easier to service. Goodluck!

It does not work well to attempt to use one fan for two bathrooms. They will either all be on or all be off. You would not be able to switch independently. We use in-line fans in larger bathrooms starting at approx. 100sf. They are absolutely efficient - no problems. They do have dampers to close them off. We install 2-3 grills in a bath depending upon size and configuration. One can go in toilet closet and one or two in the main part of the bath. We installed in a bath similar in size as yours (picture attached hopefully - been having trouble getting photos to attach) with one grill on the ceiling between shower and toilet and the second grill across the room at the soaker tub. The homeowner was skeptical but called us back to say that he could literally watch the fan pull the steam up out of the shower and the walls dried very quickly. The units come in different cfm's and should be sized for the room.

Just a thought: Consider being more creative with your lighting choices. The ceiling isn't the only place you can add lighting; why not also consider wall mounted sconces or vanity lights for a cozier feel? The lighting in those combo units is usually unflattering and insufficient for a bathroom. Also, please post photos of your space. Recommendations are typically space-dependent, so you'll get better help if people can see what you're working with.