How would someone with a deontological view of morality approach the "Fat Man/ Trolley" problem? Everyone involved (you, the fat man and the people tied to the trolley tracks) is rational and autonomous and therefore apart of the moral community. As you see the trolley coming to kill the people who are tied down you are faced with the question of whether or not to "simply use" the fat man in order to save the "ends" of the helpless, potential victim(s).
By choosing to push the fat man you are disrespecting his "ends" in order to save the "ends" of one (or more) person. But by not pushing the fat man you would be willingly allowing the "ends" of another person(s) to literally end.
So what should you do? In my opinion, the best approach would be to hurriedly explain the situation to the fat man himself and allow him to make the decision because he is the one who would be making the sacrifice. If he chooses to jump and save the others then he would be willing pursuing his goals and would most likely be a hero, but if he didn't jump then he may feel extremely guilty about his somewhat selfish decision and because of this he may not be able to fully cultivate his best-self.
If I did not have time to explain the situation to the fat man and the decision rested solely on my shoulders then it would come down to how many people were on the tracks (but that's a consequentialist viewpoint... I think?)
In the end I believe that Kant would feel strongly against pushing the fat man without his permission. Is there some way to use the categorical imperative to figure this one out? Let me know what you think.