I understand the reservations regarding parking and transportation because I have them as well. But I think you underestimate the impact, if done well, this would have for the university and program. Even 3 miles from campus it's still for all intent and purpose an on campus. It's the closest most realistic site the city dictates.
We also have no idea the deal the University would get, it's all speculation. It could turn out to be pretty lucrative and another source of cash flow for the university and athletics. I have no idea what our deal is with HRS but I doubt we are getting any cut other than part of the revenue our games generate. This project could turn out to be a year-round stream of revenue. Ruiz would obviously get his fair share but I'd wager he'd give us a better deal than HRS.
If it's done right with things to do in the area I think that could mitigate some traffic because it would stagger the number of people arriving and when they arrive. A lot will get there really early for the sports bar and hang all day. Others trickling in later just for the game, etc. And this is only considering major sold out games. Lower ACC games probably won't be an issue.
Just wait for more information before jumping the gun on it being a positive or negative proposal. However you slice it, having "our own" stadium is more appealing to a lot of people opposed to renting HRS.
Edit: if the city really gets serious about it, a metro mover from the University stop would be quite nice.