I agree with a few suggestions here, suggest a sabbatical. It can give him time to figure out things by himself and also the absence of work could be a big mot

I agree with a few suggestions here, suggest a sabbatical. It can give him time to figure out things by himself and also the absence of work could be a big motivator, that is, we engineers often find intrinsic motivation in building, designing and solving problems. Maybe giving him some time to miss that joy could rekindle it. It's good that you are looking for options and trying to understand.