Only problem with a series about Galactic Civil War would be that it wouldnt have main characters from the lore such as Skywalker and Solo.
Instead, I'd Darth Vader hunting down the last remaining Jedi's to extinction, local anti-imperial citizens sabotaging against imperial occupations and maybe even follow the skirmishes that Leia and her droid friends threepio and artoo would end up in with the rest of the rebel troops.
I'd imagine that the main characters of the lore would become more like side-characters to a whole bunch of "anonymous" characters who would start their adventures either against or for the imperial iron fist. I love to think about "The Rookies" episode done with Stormtrooper recruits, in a different setting of course.
And later on when major SW characters would start making their appearance we could have a lot of old faces supporting the story and have their own invidual stories such as Wedge Antilles and his Rogue Squadron. Of course you wouldnt have to cut out things such as Battle of the Hoth either.
Or even have a whole set of episodes forming oh-so-awesome Shadows of the Empire story, like they did with the Malevolence and Ryloth episodes.
Never ending possibilities to have a very interesting series set to the classic SW era but I dont think we will be seeing such.
I like the concept of it too. Like in ROTS, this series would aswell make that nice twist like in the saga, in which the good guys wearing white turn out to be bad guys after all.