They need to just go with Tressel as interim for a year, let the potential sanctions situation get sorted out and try to make a good hire in December. Sure, you essentially sacrifice a recruiting class, but it's better to get the right guy and deal with a lost class than hire somebody just to hire somebody and have a crap coach for three years. Plus, with the transfer portal being a thing now, it's easier to cover up recruiting deficiencies than it was a couple of years ago.
Trying to hire a coach in mid-February is tough. Going the interim route gives you 10 months to do your homework and wait to see who emerges next season. Plus it, presumably, gives you more clarity to offer with regards to any NCAA issues...which I suspect is scaring everybody away right now. Of course all of that assumes a competent athletics department...seems like Sparty might be lacking there.