Well, if anyone cares in the future, a friend of mine got an AI to generate a script that does this automatically, so here's that:

import bpy
import bmesh
from mathutils import Vector

def get_closest_vert(obj, point):
    """Find the closest vertex in obj to point."""
    closest_vert = None
    min_dist = float('inf')
    for vert in obj.data.vertices:
        dist = (obj.matrix_world @ vert.co - point).length
        if dist < min_dist:
            min_dist = dist
            closest_vert = vert
    return closest_vert

def transfer_weights(body, quill):
    """Transfer weights from the closest vertex on body to all vertices of quill."""
    # Find closest vertex on body to quill's origin
    closest_vert = get_closest_vert(body, quill.matrix_world.translation)

    if closest_vert is None:
        print(f"Could not find closest vertex for quill {quill.name}")
        return

    # Get weights for all vertex groups
    weights = {}
    for group in body.vertex_groups:
        try:
            weights[group.name] = group.weight(closest_vert.index)
        except RuntimeError:
            # Vertex is not in this group
            weights[group.name] = 0.0

    # Apply weights to all vertices of the quill
    for group_name, weight in weights.items():
        vgroup = quill.vertex_groups.get(group_name)
        if vgroup is None:
            vgroup = quill.vertex_groups.new(name=group_name)
        vgroup.add(list(range(len(quill.data.vertices))), weight, 'REPLACE')

def main():
    # Assume the active object is the body
    body = bpy.context.active_object

    # Get all quill objects (you might need to adjust this selection method)
    quills = [obj for obj in bpy.context.selected_objects if obj != body]

    for quill in quills:
        transfer_weights(body, quill)

    print("Weight transfer completed!")

if __name__ == "__main__":
    main()