When I say o-line, i really mean ability to dominate the LOS and run at will. Hall was great. But we didn't dominate the LOS in many games. He had some great runs and we were adequate up front. But we still do not have a single OL in the NFL from the CMC era (hope that changes with some of the guys on the roster now). If we are going to play b10 style football you need to crank out o-linemen like wisconsin and others...
I think of the last 2 uni games... they basically sold out to stop the run and we were not able to move the ball down the field. We would stubbornly run Hall over and over and we were not able to push them around. Also, throughout the season, it was almost always a terrible sign when ISU would run out 6 OL and 2-3 TEs and line up to run the ball... the def knew what was coming, would sell out to stop it and we had no success. we also never ran the fake and threw it in those situations. the o-line is fine. But it is not great. You need to be great if you are going to play the way they do...
To your question: I do think it will help him to be a little taller / bigger in terms of being able to stay in the pocket and make throws... But it will come down to his ability to read, react, and throw accurately. If he is able to hit receivers in rhythm from the pocket better than Purdy it could help the quick passing game. But that will depend more on his ability to read defenses and get through his progression quickly if his first read was wrong. I think this is key for any qb but i don't think our offense is a good fit for a johnny manziel style qb. our coaches want you to go our play within the offense. I think you could argue Purdy's best year was when he was just playing loose tossing it to Butler when nothing else was open. it was much harder when he had to read the def, play within the offense.