Friendship is important, especially in business. People don't always see the potential instantly, that's why I would advise you to have a sit down with him. If you want someone to be involved, involve them.

Finding someone else will be equally hard, if not harder since you won't share a friendship or similar vision that lead to the "idea" in the first place.

I believe everyone to have potential, its up to you to get it out of them—if you want a successful company at least.