As promised, I’m now watching through TBB, so I can put together thoughts for you from an editing perspective.

I’ve just started with the final three episodes of season one, and the first three of season two, to remind myself where season one ends up going as I commence my rewatch.

Thoughts:

In terms of the key plotline, season one’s focus is primarily on the transition from Republic to Empire. There’s a lot of content on that theme, all of which is fine, but much of which in isolation isn’t too vital. But, the main throughline of Kaminoan-Imperial politics, internal Kaminoan politics, clones being phased out/replaced by stormtroopers, Tarkin, and Rampart, is very good, and I think represents the spine of the season worth keeping as much of as possible.
In terms of the character plots, obviously the Batch themselves are key, in particular their relationship with Crosshair.
Thankfully, both Crosshair and the Imperial/Kaminoan plots are largely unconnected from our Batch stories, so a lot of those scenes from otherwise unused episodes can be used pretty freely.
For the Batch, they do need to have distinct and strong personalities, so I would preserve as much of the episodes which demonstrate their individuality and character as much as possible, but that doesn’t need to emerge from their more stereotypical behaviours, especially when used for humour. But I’d be mindful to keep their character in focus.
Omega is a little tricky. She’s not awful, but she’s been fairly criticised as sometimes dangerously overestimating her abilities and taking risks, as well as a little too childlike for even a young clone. She is a good character and ultimately the heart of the show, but I think we can afford to give her the Grogu treatment - allowing her to stay a little more in the background, with character development shown a little more slowly. That said, people have also noted that a lot of the time she’s left behind, later causing problems, or taken along, later causing problems. I think some of that could be solved by dialogue trims - specifically having her be less argumentative when ordered to stay behind. It might strengthen her character if she’s a little more military/obedient, as if she recognises that certain missions are beyond her capabilities. I’d imagine most of the young male Jango clones would have behaved the same during their early training. I’d still preserve all of her key moments and more valuable dialogue with the other clones about who she is - but perhaps have her a little more comfortably junior given her level of experience. I’d also have her be a bit less anxious/worried/impatient in some scenes, for the same reasons.
Cid needs to be established but doesn’t have much development, so doesn’t need to be in huge focus.
I’d seek to preserve anything that ties back to or develops other key locations or characters - Rex, Cody, AZI, Ryloth, Cad Bane, etc.
The other thing I noticed even in these six key episodes I watched, was that the show is very action heavy, even more so than Clone Wars, and, as much as I hate the word, it feels like some of their missions do contain a good amount of “padding” especially when they’re travelling from A to B within a mission. Sometimes I think whole sequences could be trimmed, removing a few steps from their plans/journeys, to get us to the meat a little more swiftly.

Finally, on those episodes I watched, I think all six were pretty vital (obviously, since they’re finales/premieres). The Gregor episode features Gregor (from TCW and Rebels) but also gets Hunter captured, transitioning neatly into the two-part finale. The very final episode of season one could probably do with some condensing, with a bit less travel and some combining of the scenes where the Batch and Crosshairs talk. As for the three episodes which opened season two, they were all pretty decent. The third episode could probably be woven nicely into the other two, since it’s a Crosshair/Cody story without the Batch, having Rampart’s execution of the clone on Serenno coming before his second scene where he shows doubt in Crosshair - doubt he doesn’t show in their first scene together.

Anyway, now I’ll go rewatch the earlier episodes with all this in mind!