McFarland was 6-0, 300 pounds when he was playing next to Sapp. Yes, he did play the 1-tech for Tampa and yes, they did use a first round pick on him. However, he was approximately the same size as Sapp, who was the size that Marinelli likes in his DT's.
So, while you're correct that they did use a first on a 1-tech... he was the same shorter, smaller, quicker DT like Rod likes. That's why I mentioned before (not this thread) that a guy like Michael Bennett (6-2, 290) could be taken at 27 and he could work in as the 3-tech when Crawford is resting or he could play the 1-tech next to Crawford in the Nickle. Or even play at DE in goal line situations.
A guy like Bennett is extremely versatile for Marinelli. A 320 pound run stopper will only play the 1-tech spot and would come out on passing downs. He would primarily be a run stopper and as Jimmy Johnson once said, run stoppers are a dime-a-dozen. Frankly, Dallas could find a big guy to clog the run lanes a whole lot later than the first round. All they will do is bring in a guy like Mincey to rush from DT in the nickle. You don't have to be a great athlete to do be a big run stopper... just big and strong. Those two traits are not rare at all in the NFL.
Marinelli feels like Jimmy Johnson in that pass rushers are the ones you draft high, not the run stoppers. As much as the passing game is dominating pro football these days, a big run stopping DT won't even play that much, and like I said, they can be found in later rounds.
Why draft a huge anchor in the first round, even if he is a good pass rusher for his size, when you can just put in Hayden or Terrell McClain on run downs and then bring in a quick, good pass rusher like Mincey on pass plays? Hayden and McClain are just as good against the run as the 320 pound guy is, and Mincey (or someone like him) will be a way better pass rusher in the nickle.
Now, if Marinelli thinks Brown is an exceptional inside pass rusher, then I imagine he will be interested in Brown. However, I just don't see the elite quickness needed for pass rush out of Brown.