I read this book sometime around 1985, it was about an agent that was capable of projecting his mind into other bodies, the stronger an aura such a person has will enable them to stay longer in their borrowed body. I do not remember the plot, but I do recall that at the end the hero in a borrowed alien body, a body that has a spinning ball for legs, is stuck with another female agent, also in a same species alien body, they both can't return to their bodies, and their final act is to mate, there was a hint that their offspring would have the greatest aura.
That's the first novel in Piers Anthony's Cluster series, 'Cluster.'
Our hero is Flint of Outworld, who is basically a green skinned barbarian. He's pressed into service as an agent due to having the highest Kirlian aura of all available humans, and that aura is what allows him to survive when transferred to another beings body. (The aura fades at about 1 intensity per day, so with an Aura over 200x normal, he can last for around six months, although illness or death of his natural body would reduce that.)
At one point he is placed in a Polarian host; they are teardrop shaped beings that have a spinning ball at their base that they use for locomotion. He also encounters an agent from Andromeda repeatedly, managing to temporarily overcome her several times, before the two of them transfer to Mintaka together as their natural bodies are killed. They mate in Mintakan form, and their descendant (Melody of Mintaka) is the protagonist of the next novel. She does, indeed, have an exceptional aura, higher even then her ancestors had.
One of the later books in the series had Kirlian in the title; Kirlian Quest.