I don’t know how slow this would be, but you could clone your character, use the ‘scale’ to make him a little larger, fit your current one inside of the larger one, and then apply your transparent flame/whatever texture to the outer guy. I’m pretty positive this would be a CPU burner, though.
For reference, the last time I tried that, it looked pretty good in the preview window, but as soon as I tried to render it, Daz Studio crashed violently. Every. Single. Time. Now it might have been that my PNG-creation process did not create PNGs that met with its approval during render, so if you’re using PNGs you already know render okay, it might work better.