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.
The problem with Federation civil war ideas is that the Federation is such a black hole - what is it really? We haven't been introduced to it enough that we would understand what the issues are if there was a civil war. It's just this nice, bland, undefined place where everyone is happy, la la la.
has always taken place around the margins of the Federation, rarely venturing into its internal workings. A lot of groundwork would have to be laid before anyone would understand or care about the Federation splitting apart.