Hi Stevie
Yes this idea of veg is good – Was thinking of growing the usual tomatoes, chiles, a caper bush, during the normal growing season along with cucumbers, marigolds. Then switching in September to winter salad crops and leaves such as spinach.
But remember that polythene does not keep frost out so citrus and other frost sensitive plants will be at risk.
Crop rotation is as desirable as outside i.e. as much as one can, but more difficult because of growing a narrower range of crops. I would not call soil ‘sterile’ when top dressed; rejuvenated is better!