That’s my plan: long Z2 weekend rides (for the entire season) and interval work during the week. Doing only Z2 base I need a minimum of 10 hr/wk in order to be improving; doing a mixed plan, 10 hr/wk max would be great.
That said, SS is not just a short version of a long Z2, it also works FTP. That’s where the fatigue comes in. You have to experiment and figure out your limits before you know what you can handle and what’s right for you.
Thats basically what I did for 6-9months. Low volume versions of SSBI/II and SustPB during the week + 2 x 1hr z1 + 2 x 3+hr z2 on the weekends. Intensity is petty high in LV plans so you get SS, over/unders, threshold intervals and VO2 intervals during the week and then long z2 on the weekend.
I found I could do low volume versions of SSBI / SSBII on Tues/Wed/Thurs but that did not work for me when I got to SusPB, especially the second half. With SSBI/II I felt the fatigue build over the three days but it was manageable. First time with SusPB I got through the first four weeks and imploded in the second four (lessons were learned.) I ended up prioritizing two of the workouts and making the third optional, but it was a little too late at that point. Later on I did a modified SusPB and only scheduled two of the three workouts and that went much better as I could recover and hit the two workouts really hard.