That is possible, but not with every general contractor (GU). They must have an extreme customer awareness down to the last craftsman. And you have to plan very, very detailed in advance and, if necessary, bring a somewhat higher "tolerance awareness." Our tiler was very good but usually works with the client on site. That means he works and discusses small details directly on the living object. For example, agreements over the phone were not his strong point. He would be less suitable for remote clients. My heating engineer, for example, is the exact opposite...
Therefore, I find the option with the retiree, who can spend 3-4 hours daily on the construction site, very good. Whether a GU is suitable for "Remote-Bau" you only know afterwards.