I guess you did NOT observe carefully the high pertinence of this design.you wrote:How are we going to have a temporary attachment and detaching pin at the centre
nothing else is needed for keeping the weight at the center of the wheel:
it is still remaining at the same place under the support of the two arms during the full rotation.
edited:
when the collision occurs the kinetic energy of the upward incoming weight is transfered to the weight previously located at the center.
In the same time the incoming weight is stopped at the center of the wheel and will be remaining at the same place, waiting on the next collision (like for the Newton cradle)