I'd be all-in on Hartline. Kane Wommack is quietly having a great start to his career at South Alabama after a good stint as Indiana's DC a few years back. You could convince me 64 year old Willie Fritz at Tulane as a 4-5 year band aid solution is a better option.
The difference in buy-out between the end of this season and the end of next season is $12million. And while that may seem like a lot, especially if they fire him after this year with his $20million buyout, it's paid over the course of his remaining contract shelf life (5 years). Indiana is about to see a major media revenue boost to start next season when these PAC12 teams are set to join. Current deal is around ~$60 million and figures estimate the new deal to be around ~$90mil a year.
Indiana can "afford" to fire Tom Allen after this year. The real question is, does Indiana actually want to invest in the program. I'm talking a brand new practice/indoor facility. A weight room that is exclusive to the football team (they share with other sports). And just an overall salary pool increase to not only attract, but keep quality assistants. You can fire Tom Allen and the next guy might be better, but nothing is going to last until the latter happens. And it may never happen.