This does happen now, but like you said, it’s usually because the thrower’s being crowded. In my proposal, that would be a foul on the marker, but the consequence would be that all markers would need to mark far enough away that the thrower couldn’t touch them. In essence, it would create a zone around the thrower’s reach which belongs to them. Any entrance into this zone could lead to contact, which would always be a foul on the marker in my proposal.
I know it seems weird for intentional contact from the thrower to be a foul on the mark, but I think the personal zone reframing maybe makes it make more sense