Best Power Pack
Ok, so it turns out that I was all worked up for nothing, though it was not my fault but those incompetent contractors' I had talked to, LOL.
All my venting problems can be solved by building a soffit inside the brick cove (that is surrounding the cooktop) and using a Power Pack, something like on the picture (see the link).
I need about 600 cfm. The only limitation is that the unit cannot be more than 15" deep (from front to back). I have looked at Zephyr, Broan, Vent-a-hood and my head is spinning.
What are the better power packs?
Here is a link that might be useful: Cove hood