I didn’t say anything about Trek in general (though by and large, no it isn’t...Treks morality allegories also come dipped in a fair chunk of Utopianism and optimism. If that’s missing, it isn’t really Trek anymore.) and I disagree that it would work with the established Picard character...he can be wrong or fallible, for sure, but the character doesn’t operate in moral grey zones as it were; his conflicts come from balancing one ‘good’ against another, and if his choice leads down the wrong path, traditionally he has faced that too.
To take the Ensign Lynch thing. He allowed his anger at the Borg to lead him into a dark place. But it was righteous anger, hate born from their actions against him and others. He doesn’t have the resources to save the assimilated crew, and he does have the resources to keep fighting what they have become. The conversation later (that should have fallen to Beverley) doesn’t change the moral status of fighting the Borg, it changes Picards realisation of where his responsibility lies (I.e he won’t win by killing every Borg standing, that won’t bring his people back, but maybe he can save who is left) and what has blinded him to this (anger, no matter how just, how righteous) The story is then resolved by defeating the Borg anyway..but only because compassion, not anger, took him there.
At no point did Picard shift into ‘morally grey’ areas. Lynch was already dead when the Borg took him to all intents, Picard fired on the Borg, not the Starfleet ensign. Just as he had in the corridor earlier, he chipped at his own soul because he had no other option.
That’s the character.
In some ways it’s the define trait of every Captain we have as protagonist in the Trek setting, it’s part of the milieu. Sisko chips at his soul for the greater good too, ditto Janeway, and even in less deeply obvious ways so does Kirk. (I can’t comment on Archer, ENT bored me amongst other sins in series one.) That’s the job.
Morally grey Starfleet captains in Trek *don’t* make for good protagonists, because that’s not the way the setting works. They do make for useful antagonists, because it’s a handy mirror. Other settings? Sure, have Captain Punisher of the USS MurderDeathKill, but that’s other settings working in their way. Let Trek be Trek. The ‘it’s more interesting If’ always says more about the individuals taste than the show itself.
I mean some of us make think Trek would be ‘more interesting if’ it was episode after episode of xenobiological porn, I mean, do Orions have dark green genitals? What about Andorians? Where do those ridges and bumps extend to on Cardassians and Bajorans? But Trek isn’t really there to go beyond slight titillation as part of its setting. It’s not The Red Shoe Diaries in space. (Though if it goes there, I am ready to pitch and I bet they can get Braga away from the Orville for that one....)