Inspired by the Proving Ground Triptych fanfic series, which condenses Hogwarts into five years of schooling and therefore also combines the year plots, e.g. PS' whole "Quirrel possession" plot is combined with POA's "Sirius escaped" plot. The second fic combines GOF with COS, and so on.

If you, as a writer, were to combine two of the yearly plots for a similarly compressed AU, which ones would you combine, in what order, and why?

 

I'd start as they did - with PS and POA. I always thought POA missed Voldemort anyways. I think it would, with Sirius being sighted around Hogwarts and with dementors, provide a good cover for Quirrell so he might not need troll and Snape being suspicious because of Sirius seemingly more threatening with breaking into Hogwarts and such. Could even have Voldemort succeed and enter the scene with Sirius/Peter reveal although that might be a bit too contrived. Of course, still no one believes he's back.

I'd continue with COS and HBP because I always thought the two had great synergy in revealing Voldemort's past. Combined, they could accurately show us the whole evolution of Tom Riddle into Voldemort. Side quest, aside of killing Dumbledore, might be retrieving the diary since the Voldemort, now having succeeded much earlier, would know what's going on and may be not so happy about it. Figuring the end of this one is tricky though. Do we have clash of Voldemorts in Chamber? We still kinda need Dumbledore if it's to stay canonish.

And then GOF and OOTP. To distract everyone from the lies about You-Know-Who, the ministry introduces a tournament, and are delighted to tarnish Harry's reputation even more once he's participating in the tournament. The final portkey with some voldemorty magic might transport Harry directly in front of the prophecy. The duel here then can be either Harry/Voldemort - priori incantatem, or Dumbledore/Voldemort - Dumbledore dies. Harry both managing DA and the tournament could be a good tandem to show him grow into a great wizard. Umbridge is somehow a judge, of course, and is giving Harry 2 points, Karkaroff is delighted.

There is, of course, a lot of problems, and even now I could nitpick thousand things that will need figuring out, but this is just in-moment thoughts.

 

Off the top of my head...

Year 1: PS and CoS - Quirrell has the Diary (willingly? forced into it?), and so his possession is by the Horcrux, with the intention of using the Stone in some ritual to unite the fragments of Voldemort's soul, and using the basilisk as a distraction...although Dumbledore would probably pick up on that pretty quickly, I guess. Meanwhile, the idea of Harry as the Heir could have more legs as nobody knows him yet.

Year 2: PoA and HBP - With the exception of Dumbledore dying. With the 'threat' of Sirius and in the aftermath of the Chamber/Stone double-whammy, Dumbledore decides Harry needs to know more about Voldemort. This is probably where you'd want to fit in Voldemort getting resurrected...maybe Pettigrew becomes a more active participant, stealing some of Harry's blood for the potion and taking it to the graveyard? Or some other location after assembling the ingredients. You could maybe work Draco's side of things in as working with Pettigrew, but equally, depends on how old they are in this version - a 12 year old getting involved in this seems a bit of a stretch.

Year 3: GoF and OotP - Umbridge is at Hogwarts for a better Ministry presence during the Tournament, and change the portkey so that it takes Harry to the DoM to retrieve the prophecy. I guess this is the one where Dumbledore dies, maybe wounded in his duel with Voldemort? Or Draco takes advantage of the extra influence Umbridge (unwittingly?) gives him.

Then I guess two years to cover the war.

 

My personal take on it is the following:

Year 1 is PS and POA. It's a combination that just makes sense - have Sirius escape because he sees that Harry's about to attend Hogwarts. The difficulty here is combining Quirrel and Lupin, but I think I've got a way to make it make sense: just have the POA conclusion at, or before, Christmas. Remove the Norbert plot and some other stuff to make it fit. Sirius escapes, Lupin is outed as a werewolf by Quirrelmort (though everyone thinks it's Snape). Dumbledore's absent at the end of the year to try and get Sirius declared innocent, during which time the PS conclusion plays out.

Year 2 is COS and HBP. Partially because HBP is a little thin otherwise, partially because they've got plots that focus on Voldemort's past, partially because both are about blackening Harry's reputation. In the same way as Shinysavage though, I wouldn't have Dumbledore killed at the end of the book, but instead just have him wounded by a more successful Diary Horcrux and slowly dying as he was at the start of HBP. The Diary Horcrux manages to escape also (wearing Lockhart's body).

Year 3 is GOF. The international focus of GOF is always going to be awkward to fit in elsewhere, I think, so it gets its own year. At the end of the year, Voldemort's shade absorbs the Diary and the Diadem, forming a fucked-up Voldemort Voltron that effectively functions as his resurrection. Dumbledore succumbs to his wounds, going out in a blaze of glory against Voldemoltron in a confrontation that leaves the Voldemort Collective with psychic damage that prevents him (them?) from knowing where his Horcruxes are because I want to make the next year's plot work.

Year 4 is DH and OOTP. Harry is hunting the Horcruxes, but so is Variegated Voldemort. In the meantime, Harry is gathering, and occasionally losing, allies as he tries to learn the last bits that Dumbledore wanted to teach him. End on a big battle yada yada, Harry is the final surviving Horcrux and is nearly absorbed by Voldemort, except that the protection kicks in a final time and burns Voldemort to ashes from the inside. Or something, it's all rather off the top of my head.

Not entirely satisfied with this outline, honestly - having a heavily Voldemort focused year as second and Voldemort being largely absent for three is weird considering the hunt for Horcruxes occurs in four. But this more or less makes sense to me.