After the season is over
Horford, Alexander and Dort
2021 & 2022 1st round picks, Siakam and Baynes
Flynn/Trent (or FA)/Dort/Boucher/Birch
Toronto - Horford contract is cheaper and less years compared to Siakam. Won't be getting top5 pick anyways so trading 2x 1st for Alexander and Dort is nice. The time Horford contact is up we can resign Alexander. OKC - Unloads Horford contract, Baynes contract isn't guaranteed next season and Siakam gets a new start. Gets more 1st round picks.
I would do the Carter trade 10x over before I do this trade for Toronto.
Ideally for you we are gonna be giving THEM 2 FRP (one a guaranteed lotto pick) for the pleasure of taking on Horfords awful contract and 2 role players. Not to mention we are giving them the best player in the trade. All around awful for Toronto