We can still do that and not need the field upgrade by winning the conference every year.
Besides, it's going to be extremely rare that an at-large Big XII team doesn't have at least 4 at-large SEC/B1G/ACC teams ahead of it.
If the format changes and the odds of hosting increase (as mentioned about by Cyclones500), maybe look at it then, but right now there are SOOOOOO many better ways to spend that money.
It's my understanding that the moisture in the ground is the problem. The one ad-hoc solution I've seen is covering the entire playing surface with a giant tarp and position jet heaters around the edges to pump a ton of hot air under the tarp. We could probably do that, but I suspect moving the game to US Bank is still more feasible.