I really like Havertz and think he'll be great in this Arsenal team.
Transfer after transfer Chelsea keeps making even less sense, their midfield and striker options are horrible.
People might think 'OK, they will buy a few players' - sure, they might. But they cannot bring quality players without CL football so I don't expect them to fill these spots (Havertz, Kovačić) with better players.
Yeah, Kai Harvertz for Arsenal would be great, when I watch him play, who I really see is Mesut Ozil, They lacked strength but they're really both technically smart and tactically ready especially during big games. I don't really know Mikel Arteta's plans for the new season, but I'm sure they'll make a gream combo from Declan, Kai and Odengaard.
Chelsea has lots if players to replace, Brighton Caicedo would be a good replacement for Ngolo Kante. With Mason Mount wanting to move, still not certain though they ain't have agreement ( Chelsea and Manchester United ) Plus replacement for Kovacic and Kai is something that can't be replaced this season, they'll struggle if you ask me. They've not Madea good signatures after all the push outs of these players.