Not part of the plan is not the same as impossible.
Couldn't he have stayed healthy and worked to CURE leprosy?
If he had no talent for that, then make money and fund those with research skills?
I believe Father Damien's calling was to work with lepers, he placed that above his own personal welfare. Mother Teresa worked with lepers for nearly half a century and never contracted leprosy.
To the best of my knowledge leprosy is treated with antibiotics and steroids, neither of which were available at the time. I do not believe that there is an actual cure for leprosy.
I see no appreciable virtue in throwing away one's (God given!) life mucking about with contagious lepers.
Granted, I'm not terribly compassionate.
But hanging out with lepers is an affront to good sense.
Read Matthew 25:31-46, throwing away one's life is a matter of perspective.
36Naked, and ye clothed me: I was sick, and ye visited me: I was in prison, and ye came unto me.
Not a word about throwing your life away among the terminally contagious though.
I do see your point however.