Re: New Character Idea...
Couldn't you just build the entity, then give it the power of no range Mind control, the mind control having a custom disad of needing to physically merge with the victim to be used, then the nanointegration could just be a special effect of the power? at first the mind conrol would be strong enough to affect commpetent norms, but through the campaign it may become strong enough to take over superhumans(gaining ep). in this manner it would have control of the body like a rider has control of a horse, but could still use its own actions...?
The other way I could think of would be to build a template of a possessed being by the arm and give the arm a summon only usable with a focus(prepaired human body) and the summon would be the template. You could build several different templates in this case and give the summon more power to summon a defined group. you could then build different stages of integration int the templates, the first stage the summoned MOUNT or human Vehicle still having its human frailties and stun end etcetra, maybe the later stages of integration being more like a AUTOMATON that takes no stun and has superhuman attributes die to the invasive conversion the entity has caused in the now DEAD body. again the entity could control its body like a mount or vehicle if you so choose with ego rolls instead of riding rolls.
just shooting out ideas. Hope you find a way that works:D