Fun fact: JJ Watt entered college as a TE. He was 220 coming out of high school.
Now, Hall is not quite at Watt's level. According to the 3 Sigma theory mentioned earlier, Watt is in the top 5 of the most athletic football players of the past 15-20 years.
That being said, Hall seems well-equipped to succeed with extra weight. What is he as a pure edge defender? He's slower than average, doesn't have great hip dip, doesn't have elite agility. His best attributes are his strength and length, which he combines with above average athleticism for that size. If he added 20 pounds, I think he would accentuate his positives by being far more athletic than average for that size, and his length and relative flexability would give him a massive advantage for *applying* that strength in the variety of wrestling moves that one has with offensive linemen. It's one thing to be strong, but it's another to be able to apply it.
Anyway, I was thinking of Hall as more of a 4 or 5 tech. He could play 3, surely, with that extra bulk, particularly on passing downs when you might want extra speed on the field.