You can imagine a lot of things. Failing the in-PRT just means rolling until you pass.
To the original poster--decide whether you want to be a Naval officer before you put in a BDCP application. If you can't decide now, then wait until you graduate and put in an application to OCS. The deal is this--if you want to get commissioned through OCS, you will. If you're not sure if you want to, but want to give OCS a shot, then don't go BDCP. If you come in off the street and quit, then you go home; no harm, no foul. If you want to take the Navy's money (and BDCP is a significant chunk of change), then you've got to expect that you'll have some kind of committment. But don't think that they'll take the commission away from you unless you're a complete dirtbag. If you go to OCS, do what you're told, and keep a decent attitude, you'll get through. The ones who fail do so because of flagrant and repeated violations of simple rules.
A word on rolling at OCS. It is by no means a punishment. Most people in H-class are there for medical reasons or for not passing the PFT. People in H-class have a bum deal in that they're not progressing in their training, but no one goes out of their way to hassle them. In fact, the current MGySgt at OCS is as fair a man as you'll ever meet and treats the H-classers with complete dignity (i.e. say anything to them except encouragement and he'll skin you alive). So don't let that be your fear. Rolling can be a challenge and setback, but you'll have those your whole life, no matter what you do.