You might be able to do this, but it may not be a good idea. The goal with exhausting rising cooking effluents is to move them out in a straight direction, with as little loss as possible and without bends -- or doubling back down and out the floor. If the structure of your house allows this, its probably better to add the hood above that you want and route new duct either up (out the roof) or horizontally (out an outside wall). This will likely be more effective than the old downdraft (especially for stockpots or taller pots), which you can easily close or block up.

The hyex is the blower? I think it's possible the silencer may not be so necessary ... I also think people who know about this may tell you that it is! Here's my experience. I just bought a 42" x 27" undercabinet hood with no blower and routed the 10" pipe up to the attic. It bent there at about, um, 80-degrees and the HVAC guy put the silencer in at that point and then added the fan. It was loud. So instead he added some more duct parallel with the ceiling which pulled the silencer further from the hood itself, if you follow. It got quiet. My HVAC guy, who is admittedly a nut, seemed to be of the opinion that the biggest reason for the improvement was simply the increased distance from the hood. I also talked him into making that extra duct run parallel to the ceiling - i.e. at a shallower angle than right-angling it straight away after it hit the attic; that may also have helped (he was a little reluctant because it was extra work but he's a really good guy and wanted very much to do a good job so when I turned around he'd done as I suggested: yeah!). So anyway, that's what this guy said - he's of the opinion that the silencer was "a waste of money" and the proximity-parameter was of biggest importance. I talked extensively with this amazingly nice guy at Tradewind and I'm pretty sure he would not agree; he'd credit the silencer more. If you have time and patience, I'd say you could try it without and if it's a problem, then get the silencer and pop it in. Just so you know, that silencer is *massive* - it's more like a jet engine than the blower itself. Good luck! BTW, I hope you don't have fussy neighbors too close. I opted not to use an outside blower because I was concerned with the noise it would impose on nearby neighbors; others have noted this problem with that blower I think. If you're miles from the next elk, it may not matter. If you have cranky neighbors 20 feet away, well...it seemed a problem worth preempting.

yes, they actually sell vent hood wall switches, depending on the manufacturer. you just need to make sure your model is compatible. for example, my vent fan is made by fantech. and they told me i could wire it to one of their wall switches, linked below. though i think you would need to wire your lights onto another switch and the fan on another, but usually they are wired separately anyway, so this won't be too difficult for an electrician to do. the concept is similar to those in-wall ceiling fan switches. Here is a link that might be useful: vent fan wall switch

Tyler, so how is it going with the cooktop/hood? We are planning a remodel and considering a similar situation. We are in Florida, so I’d like to avoid MUA if possible as it is painfully humid and hot AF here 360 days of the year and one of my main goals of this remodel is to keep the hot air out. We have an older 1959 home, 94” ceilings. Our kitchen designer wants to put a 36” wolf gas range-style cooktop in front of a 104” window with a 6” backsplash/ledge using a wolf or zephyr 48” ceiling mounted hood at 600 or 700 CFM. So if the cooktop lands at 36”, that puts the vent 4’8”away from the countertop on the ceiling. I’m looking for functionality of suckage (sorry, I never made it past geometry into trig, so “suckage” is as good as it gets for me—lol) and if I have to use a different island hood that hangs 36” above the cooktop, so be it. I’m curious how it’s going for you, especially cleaning the window after cooking. Is it a daily chore or weekly? (I don’t see the window as a cleaning issue, when I cook, most of the splatter winds up on me or flies sideways, but rarely backward—but I’ve been wrong before, and I’ll be wrong again). I just don’t want to make the hood mistake. Any and all input is appreciated ;)