However, our remodel presents a job I haven't seen discussed before. The foto shows the current setup; we'll be refacing the cabinets, changing appliances etc. The venting situation is currently weak at best (recirc through microwave) and I'd like to improve it if possible, with a caveat being I'd prefer not to use the downdraft vent option.

The cooktop is on an interior wall in a kitchen with a 12 foot ceiling, where the wall does not go up the entire height (note 2' - 3' gap shown in foto). There is a channel that runs along the top of the wall but it's only 9" or so from the wall in depth, which means there's very little room for a chimney stack to come up since many of them have 8" ducts and have a total of 12" - 15" depth in the flue extension (please forgive me if I do a poor job of describing). I also don't think it would look good to have the exhaust ducting running on up into the ceiling.

I don't want to duct into the wall and down since that would mean a 180* curve to get the exhaust into the basement and then another 90* turn to direct it towards an outside vent.
In fact, can you even vent into the wall and down or is that just too much of an engineering challenge and/or load to put on a fan?

Anyhoo, I do have a remodel professional taking a look at it later this week but I'm looking for ideas to bounce off him. Quite frankly I'm stumped but I don't do this kind of thing for a living so that doesn't say too much.

TIA

Use a square or rectangle vent going straight up.

You already use decorations to "difuse" the visual appearence above the cabinets, so why not continue the practice?

Dimensions are not stated, yet MW's are typically around 24" W. Choice of your cooking appliance will discuss venting cfm's recommended by manufacturer. Knowledge of your local codes and specs pre-purchase is good. Merging into the overhead channel, covering with wood and crown seems plausible. For symmetry, you might consider doing the same down the run with another cabinet. I do note you have a curved door to the right which offers some incorporating design symmetry possibilities.

With that in mind, I'd like to ask snoonyb which manufacturer they recommended for a moderate price yet good mechanical design endeavor of essentially custom venting?

Good luck OP.