Either the original Advanced Healing field or the updated Voltage Repair field can be used by people with long term illnesses, but you need to take it slow so you don’t overwhelm or overtax your system.
I’d argue that someone with long-term, chronic illness needs something like Voltage Repair (or any other field that energizes the body) to get energy back into their system so the body has a chance at healing. But, since the added energy from Voltage Repair is combined with the rapid healing rate from Advanced Healing, you have to be cautious and take it slow.