Your poor DS, Thea. DD was rejected by all 4 last year. Thankfully she has turned out to be a really resilient and resourceful young woman and she had plans B to D already worked out. I'm so glad it has paid off for her as the tension was becoming a lot to cope with over the last few weeks.
As regards academics for re-application, I don't really know. DD had 9 A* and an A at GCSE, and 38 points (6,6,6, 6,6,6) at IB, A at A level Maths and is doing an A level in Biology of her own accord this year (at least AS biology was a requirement for at least two of the universities she applied to this year (vs the ones she applied to last year which did not require it).
She decided to do the extra A level both for the different universities but also to keep her hand in so to speak. I'd imagine it might be a good idea to do something academic and preferably scientific in your year out if you intend to reapply.
The thing she also found that was really important was to be sure that the school reference was really, really good and that they know what they are doing. Her first one from her state FE college last year was a bit shit quite generic. She's doing the Biology at a "crammer" (she's the only non-retaker in her class) and they really know how to write the reference- they pulled together information from a range of people- her former tutors etc and produced a thing that was actually fit for purpose.