Responses
He wants to use Maya as his body since he can't move that much due to his illness. That's all there is to it. His ambition requires him to do heavy work and that is why he thought that if he could recruit Maya, he could use him to do the heavy job instead of him.
That's it from my understanding.
agreed. He wanted to live though Maya
But what were Ruka's real intentions, we got a bit of his thought dialog but i didn't understand his goal （￣へ￣）