That would be like a mosquito thinking it could pick up a rabbit just like a hawk can. Downdrafts are virtually useless. If they are actually strong enough to pull down the HOGS, then there goes your flame too, and it takes 35 minutes to boil that pasta water.

An overhead vent is the only real choice with a high BTU range.

There are only a few brands that are "okay" with putting a downdraft behind a full size range, and even in those situations it's going to be ill advised. This setup in particular is an even bigger no no depending on the Thermador "Pro" range, as the Thermador "Pro Grand" is deeper than your average range, and downdrafts are really only designed for drop-in cooktops. The Best Cattura is going to be one of the better units, but I still wouldn't recommend it in this situation.

What it's going to come down to is that if that downdraft in any way causes issues in conjunction with the range, Thermador is going to wipe their hands of the situation since they already advised against it. This can be things like the ventilation pulling the flame and creating uneven heating, or just ineffective ventilation in general (those front burners definitely are not getting their smoke/grease/heat captured). If you do any high heat/grease or smelly cooking, expect those smells/heat to linger and expect to have to clean surfaces regularly.