Before my lasik, I thought about doing one eye each way since I wore bifocals. They said the problem that some people have is loss of depth perception. I went with fixing my distance sight.
That being said; a lady at work had one done each way and has no problem at all.
Also my sister wears one distance and one reader contact and has no trouble.
Your friend needs to talk with a reliable provider and then decide for himself. He is the one that lives wth the decision. Good Luck.