What was the intent for making Rem sacrifice herself for Misa? We know Light is clever and smart and almost devilish? But I don't understand why Light wanted Rem out of the way?

What was his motive and what would have happened if it went wrong?
Because Rem threatened to kill him should anything happen to Misa Misa. If he planned to use Misa Misa as a tool and perhaps sacrifice her eventually. He would have to get Rem out of the way.