In terms of early celebs, someone like Colin Jackson could be a good shout, he did DOI in January and made the final of that so is obviously still in good shape. I think it depends on the celeb's background, whether or not they've kept dancing and whether or not they're in shape. I think it's quite telling that some have dodged Christmas specials whilst others have been game to do it and most of them did fairly well.
Danny Mac & Oti are non-negotiable for me as is the inclusion of Harry Judd (Nadiya maybe? She'd do great ballroom with him!). Louis Smith has kept up the dancing (even winning The Masked Dancer) so I reckon he'd be much better than he was in 2012 if he did the All-Stars and probably a contender (Katya for him IMO).
Would also like a couple of Janette's partners to come back for a shot with another pro, same for Karim with another partner.
For the women, some of Gio's partners would be a good bet, I'd give him Rose or Debbie again (his two best partnerships IMO) and maybe Faye with another pro. Who could get Gorka? I think the bridges are burned with Alexandra. Maybe Maisie but I don't know if they'd have enough spark for an All-star season. And what about Johannes? I wouldn't say any of his partners are high up my list but is there a past contestant who can match his energy. I'd like them to try and get Alesha & Kara again and maybe another shot for Pixie Lott (with Kai?). Caroline Flack would have been a great addition.