Sounds a bit like a major project. Setting the cooling section to blow air into the grill and also maintain the smoke, will be difficult. I think that this technique needs the nitrates for proper safety. These are used for air curing meats, and I would suspect fish too. The smoking might take a few days or more to finish, and the cost (electricty) of running an AC outside in the hot summer with its heat side blowing out more heat, and the cooing side just barely keeping things cool inside a small grill, and competing with the temps that the grill can get inside even if its not running... A 12,000 BTU is huge for this. Maybe a 500o or 6000 would be better, smaller, and less expensive to run. Your not really storing the foods in a cool environment to smoke them, but smoke itself must also be cooled, without its particulate condensing too fast, so your almost aught between a rock and a hard place.

I have cooked on all three and the TEK IR is the only gas grill that cooks as well as charcoal. It's advantages over charcoal are that it is quick to set up, easy to clean up and does an excellent job of creating the charcoal taste. As many here know, the flavor is created by the smoke from the fat striking the hot surface be it charcoal or something else. The higher the IR energy (from gas or charcoal) and the less the flame, the more smoke generated rather than being turned into additional flame. The TEK creates a great deal of smoke because the IR glass sits between the flame and the dripping grease. On older style IR burners there is still an open flame to ignite the grease drippings reducing the amount of smoke to add flavor. With charcoal, once the embers are glowing red, it is emitting a lot of IR and much less to no flame and hence produces a lot of smoke and flavor. I have owned the FireMagic and I would not purchase another. The burners are cast SS but they still do rust over time and the flavor grills wear out too. They are very hard to clean and the heat was not anywhere near as good as the advertisements. If you are the type that never clean a grill and don't mind a gritty looking grill it may not matter. I am the type that wants it to look clean and inviting each time and the self cleaning feature along with the dishwasher removal panels makes the TEK a breeze to clean and keep looking nice. For me that was worth a lot. The more conventional grills like the Firemagic, even with their ceramic infrared burner are not even a close match.

My understanding is that the silencer has to go before the motor (i.e. vent liner --> silencer --> motor). It's silencing the fan and motor noise, so it wouldn't make sense to have it after the motor. If you have enough space in the attic to put an inline blower after the silencer, then you wouldn't need an external blower. For us, the silencer barely fits between the attic floor and ceiling, so we had to have an external blower. The contractor was worried it would be loud outside (it's on the slope above our deck) but it's fine.

I'm on the side of open burner gas. I think the optimal arrangement is a range top and separate wall ovens. If you have to have a range, I suggest the BlueStar due to the burners. You use those more than anything else on a regular basis. To answer your question about open versus closed burner, open wins hands down every time. It's not difficult to clean. In my past, I've had open burner Wolf, Viking and BlueStar in a residential setting. My closed burner experience was with Thermador. It's been quite the adjustment moving from a BlueStar range top with open, star-shaped burners to much lower power Viking round open burners. I miss the BlueStar. I will also opine that while power is important, the shape of the burner is the most important feature. I don't like using the griddle in a residential setting. I find myself pulling out my old griddle pan. I go out side to the grill. Both features make a big mess inside and I don't like having to clean them up. Grease gets everywhere. That's my personal preference. You have to make that decision for yourself. Most people only see one of these in the showroom when it's shiny and new. Use it for a few years and see how they hold up. I do use the griddle burner for a warming tray. So, it does have a use. I don't think you need to dedicate a burner side for a grill or griddle. But, that is just me. I loved my BlueStar and I miss it.