I am not familiar with the “semi-polarized” approach so won’t comment on that.
I have had weeks with four days of training and I tried to manage it with a longer workout on one of the days (over the weekend) than increasing intensity.
Depending on your training background and if it is feasible, can you do a strength session in the morning and an aerobic workout in the evening? This might allow you to train for the same hours over four days.
If am/pm sessions are not possible, then I would do one strength session and three aerobic workouts over four days with rest/recovery days in between. Hope this is helpful.