For a Low Volume Plan with 3.5h available, I think Seiler would suggest to do one long ride of 2hours and two short Rides of 45min (one of those in Z3). No rest weeks needed or only 5/1.
In general I Like that TR Sticks to seilers approach. He is the Mastermind behind this approach IMO. Also referring to 4/8/16min Intervals is valid. I would onkly think about implementing 30/15 intervals. In some interviews he said they would be valid. However the Z3 Sessions are supposed to be hard frome the beginning. I would rather see an increase in number of Intervals (e.g. 3x4, 4x4, 5x4) than starting with a very low Intensity. According to Seiler the goal is to accumulate time around 90%HR max. That will not happen with 4x4min at 105%.