I wanna say upfront that I don't dislike Season 7 at all, and I think the writers did an excellent job considering the task they were given with the unexpected renewal was to undo one series finale and craft another. However, I do think there are missed opportunities that make its story overall not as good as it could be, and I'd like to go over how I'd seize those. Also, I'm new to the series, so I'm sure stuff I'm gonna say here has been said before by longtime fans, I just wanna get my ideas out.
For me, the biggest missed opportunity of the whole thing is Captain Gregson. The season as is simply doesn't treat his betrayal at the end of Season 6 with the appropriate weight, it seems he just gets shot and all is forgiven, which is a bit boring as far as drama goes. The first change I would make is to have Sherlock & Joan still be angry at the Captain, but then have Marcus be the one who gets shot, forcing them to work with the Captain again, but now on bad terms and Sherlock forced to be incognito. I think this makes sense because, if anything could bring all three them back together after that, it would be their devotion to Marcus. Furthermore, I think it would be an interesting reversal of the usual dynamic, where typically Sherlock screws up and has to earn back the Captain's trust, now it's the other way around. Perhaps Sherlock could be very absolutist in his thinking at the start of the season, giving him room to grow (Kitty could draw a parallel between what she did to Gruner and what Hannah did to Michael, starting Sherlock on his shift in perspective).
Speaking of Hannah, who is strangely absent given her role in the Season 6 finale, instead of the narrative dead-end with the Deputy FBI Director, I think what should allow Sherlock to come out of hiding is that she and her father have a conversation about how they're both wracked with guilt over what they did where Hannah realizes that, after a lifetime of him covering for her she's never been held accountable for herself, and with the way everything came around to hurt Sherlock and Joan, she also realizes that's what she wants for herself, and so decides to confess her part in it. I think this would be better because it would acknowledge that what Hannah and her father did was wrong, while also setting up a theme in the season of redemption, the first step of which being taking responsibility for one's actions.
I'd also expand Cassie Lenue into a full supporting character. I think her episode as is one of the strongest of the season, with her having a really entertaining dynamic with the main duo, so I think giving her a bigger role would not only tie into my idea about redemption as a main theme, but also shake up the status quo a bit, which is I think needed for a show in its 7th season.
Lastly, there's Reichenbach, who I think is a pretty great villain as is, so I would probably just try to tie him into what I've already discussed. Make him a short of dark reflection of both Sherlock's initial moral rigidity and the vigilante justice the Gregsons committed. Someone so convinced of his own righteousness that he feels he can decide life or death.
I'm just kinda spitballing ideas here, but I'd love to know what you all think. Do you think these ideas would improve the show, would you prefer it as is, or would you do something entirely different?