It could be done, and faster than you think ... but you need just the right guy ... and those guys are really scarce. Someone in the mold of a John Hart, who can impose his will on the program and get buy-in from everyone: players, parents, administration, community.
So who is that guy? You halve the turnaround time of the program if you hire someone with real big program head coaching experience, as opposed to an energetic young guy who has been successful on a relatively smaller scale. You’re talking about fixing a whole program, not just a team.