The indoor facility is going there so they can save money on redoing the east side.
Like to cover up how shitty it looks from the perspective of someone walking toward it now, and not caring that it'll still look shitty to the people who get past the practice facility?
One of my earlier thoughts was to build the facility right into the shitty back of the stands and do something like what you're talking about for non-football team'rs to access the stadium through it, or to demolish the entire upper deck and build the facility in a way where the east side of it is for football practice and the west side of it is for football watching.
But I'd still say to do the facility and separate practice field in the obvious most functional spots for football team things, and to separately make the east side not look shitty.
The best move on that last part is to travel back in time and build one cohesive football stadium at once. Short of that, demo the existing east side and replace it with a mirror image of the west side.