I don't think one could become a Sanzo against their will.

[ He hopes, anyway. He really hopes he hadn't done that to his precious son in the last few seconds of his own life. Had Kouryuu been willing to take on the burden? Had he--

Koumyou's usually-serene expression looks a bit distressed for a second there, until he gets control over his own spiraling thoughts. No. He's not going to think about this right now. ]

...At least... I hope not. The weight of that karma would crush someone not willing or ready to shoulder it.