I'm interested in what type of sealer you would want to use in food safe environment? Block would make a build a lot simpler. A few folks here have tried a block smoker only to have moisture be a problem. You have to drive out the moisture before you can build heat. True, a large fire would do that, but most home smokers will not be that big or have that large a fire. Interesting thought though.
On another note, you have to think that most restaurants will keep a smoker going 24-7, so there is no chance of moisture build up like our outdoor family smokers. On the other hand, block will break down over a period of time due to heat. Firebrick are designed for heat.
I'm a fan of foiling at 160F. We sell a lot of what we smoke. In a pinch, I will run the smoker up to 275-300F with no issues. Of course, if you want it to get to 200F, it take forever when you are working to a time line. :-) Pork comes out tasting just as awesome.
The bottom line is, if you got a fire under it, its going to be the best pork out there. Fire and smoke gives you a flavor that can't be matched by any other.
I'm not saying anyone one way is best. Find what works for you and build a fire under it.