If by some miracle of timing, the Renaissance hotel went under or decided to sell its attached building to Rogers, they could demolish the hotel portion, opening the outfield to the city. The fixed dome on the north portion would need to be reclad in a transparent material to allow natural light in. They could deck over the portion of the rail corridor between the bridges and turn it into a park for the general public to watch the game on outdoor screens. The city could expropriate or land swap the lowrise office building north of the stadium to bring the park all the way to Front Street, reconnecting the SkyDome directly to the city.
If these things were to happen, the SkyDome would be on its way to feeling more like a ballpark than a stadium.
Further improvements were as you said, bringing the seating closer to the field in a diamond configuration. Patio areas, standing beer gardens and bleachers in general admission areas and concessions on the outside instead of in the concourses would allow people to watch the game while wandering around the ballpark for food or different views.
The outer walls of the concourse, now freed from concession stands could be open with windows to the exterior, allowing natural light into the concourses and views of the city afforded to those walking about. One final change: remove the ticket booths from around the perimeter of the stadium, opening it up so that people walking by on the outside could catch glimpses of the field and of the sports fans walking about inside the concourse.