Is my student’s parallel selves exercise to ask their help in doing a Lightworker Healing Protocol session something that could be helpful and productive?

This is something we would not recommend people engage with. The reasons being that the shadow selves are parts of the mind that are in a state of fragmentation to varying degrees, becoming separated from the whole, and are more prone to harbor aberrant thoughts and beliefs. They need to be reckoned with primarily to provide healing for them, but doing a Protocol session is not the best time to invite them into the cockpit, so to speak, to play a role in carrying out a high-level healing exercise in partnership with the divine realm. They will be aided by the Protocol work because the Protocol requests assistance for them, but that is not the same thing as seeking their counsel and tuning into their energy and allowing them to have a role to play when carrying out the steps of the Protocol. That is inadvisable because when there is fragmentation, it is an aberration resulting from trauma, and that part of the mind will be less capable being only an aspect of the whole.