A raise and a 3/5ths reduction in expected hours would be one hard sell.

I once managed a 50% raise and a reduction to a four day working week, with one of those days remote. I patted myself on the back a lot for achieving that, but I was cheating, a bit, because I went from permanent to contract with the same company.

Not very strangely, the reasons that I wanted to leave my permanent position at the company in the first place - terrible, confused, and often obnoxious management - still hurt just as much even on more money and with fewer days. I quit again for good after another three months.

Only if they find someone cheaper and equally productive.

You'd be surprised what stupid managers would do. They could just fire him out of spite, and hire 2 people to do his work clumsily but "keep proper hours".

Those aren't the kinds of managers you'd want to work for anyway.