I mean, so does the canon. At a certain point, I just don't think internal consistency is all that important. In fiction, telling a good story is most important -- and for the purposes of a message board discussion about how various political systems could work, I think it's fine to pick and choose amongst non-canonical works in addition to canonical works.
I really don't think those sorts of hegemon/client relationships amongst planetary populations are the sorts of things that you can hide. Like, nobody looks at the relationship between, say, Russia and Belarus, and walks away imagining to themselves that Belarus isn't under Moscow's thumb. Even less overtly imperialistic relationships can't really be hidden on a national or planetary scale -- nobody's surprised when the Anglosphere nations back each other up in the U.N. These kinds of relationships aren't even possible to hide at the regional/sub-national level -- everyone knows the Rust Belt states tend to vote as a bloc, everyone knows the Deep South tends to vote as a bloc, everyone knows the New England states tend to vote as a bloc.
So realistically, everyone would know if, say, the Planetary Republic of New Texas, comprised of the descendants of settlers from Texas, Earth, were likely to closely align itself with or follow orders from United Earth upon joining the UFP. And if they so chose, the Federation Councillors for the Andorian Empire, the Confederacy of Vulcan, the United Planets of Tellar, the United Rigel Worlds and Colonies, and the Kingdom of Arkhen could simply vote not to admit.