I had a concept for a possession free spirit that takes people over to heal them.

This could be done with a medkit, healing spells, regeneration, or as a lest ditch effort the Life Pact.

Life Pact: The free spirit’s life force is tied to that of the character.
The character can maintain his own life by drawing on the
life force of the spirit—but he loses Karma in the exchange. The
character may spend a Complex Action to heal 2 boxes of Physical
damage, but the spirit siphons away 1 point of Karma in return.
The spirit does not need to be present, nor is the spirit inflicted
with the damage.

I came to the conclusion regeneration is fairly useless to the spirit its self because with its immunity to normal weapons at a high value for the most part it is magic damage they need to worry about. Plus it is so very very expensive. 5 power points. Useful for just jumping into somebody and healing them if it is not physical damage or caused by a vulnerability they have like with vampires or shapeshifters. Still it is not a good choice because regeneration is all they would be able to do because of the high BP investment.

Healing spells are always good,

Then there is the medkit.
I thought it would have some advantages because it is like a skilled surgeon is right there with you no matter where you are. But even with
6 in medicine
6 in logic (could be higher)
+2 specialty
+6 medkit
Bad (combat, bad weather, swamp) –3
That is a dice pool of only 20 minus wound modifiers if the spirit is possessing to make use of their body.

If they were a materialization spirited they would do slightly better by avoiding the wound modifiers. But they might then get the Uncooperative patient –2 modifier.

Basically it is nice to be able to move a highly specialized skill around so fluidly but this ends up not being the best way to do it. A rigger can use tacsofts and autosoft medicine (Assistance +1 per skilled assistant (max +3)) programs to aid them more than the Uncooperative patient (–2) and Applying medical care remotely(-2) subtract.