For the next Trek captain I vote for Gina Torres, from Firefly and Angel, she has a command feel and can be sunny or dark as needed.
Insurrection nicely set up a series that could have revolved around an internal rift within the Federation. Rather than looking for a new enemy for them to face, they could have had a civil war or sorts.
Gene Roddenberry already came up with the idea of a Federation civil war and its aftermath. That series was called Andromeda...
Pull some ideas from both Andromeda and the Star Wars sequels. In Andromeda, one of the stated reasons the Nechians revolted was the government and the fleet stood aside (ala prime directive) as a planet was invaded, subjugated and the population eaten. We've seen Star Fleet captains and crews irritation with the Prime directive before, a new federation council policy to harden the prime directive, leading to a series of incidents, certain member worlds and parts of Star Fleet revolt. That's the Andromeda part.
Princess Leia: "The more you tighten your grip, the more systems will slip through your fingers."
The Star Wars sequels without the sith lords, the (former) federation divides into multiple factions, some return to "the old" federation ideals, other try to reassembly the federation using politics and force. Still other built new political states. Star Fleet also fragments. This is what we see over the first season.
The question is where does our hero ship stand?
And does everyone on the ship stand together?