Forgot about that S-rank healer. I don't know if Jinwoo knows about him or can sense from his remains he was a healer.
However, by fighting the ant king, he saw how much regeneration capabilities it had.
The hybrid idea was that Jinwoo uses that power (after some stealing/combining spell) on Cha, with consequences down the line.
I don't know if he can shadow the ant king, would work too. Would cause some drama too as Jinwoo instantly becomes the defacto most powerfull being and most dangerous too.