Week 7: Big Sky I don't think extra bleachers would be practical or feasible for one game. I think a lot of fans love to sit in the grass areas too. However, if it was raining, sitting in the grass would not be fun.
I've heard there is a capacity restriction by the Fire Marshal but I don't get it especially compared to how we used to pack The Toom to the point that the bleachers were bending and the crowd standing 6-10 deep around the track. For one, there's nothing to burn or break or fall on the fans at Aggie Stadium. Exiting the stadium in some unforeseen emergency (earthquake or bomb scare etc) would be swift and easy given the open layout of the stadium. There are lots of exits and some fans could even exit onto the field and through the tunnel easily as well.
I think it would be easy to get 12,000+ safely in the stadium. If the safety officials think that's a problem they need to visit a lot of other stadiums in the country that seat thousands more and are much more difficult to exit in an emergency and they are considered safe.
Heck, we were packed in like sardines when I was at the Big house in Michigan a few weeks ago (over 111,000). They pack the fans in so tight that you are shoulder to shoulder but it's all good and the fans love it. Our Athletic Department needs to look into allowing more fans into Aggie Stadium if we have the demand.