This is funny. I just read a Tom Clancy novel in which the Russian Federation joined NATO. Something I do not see at all in the near future.... much like the Klingons joining up with the puny humans.
An interesting question. Unfortunately I cannot give any canonical examples, so I have to stick to speculation, but the general doctrines and behavior of the Federation give some clues.
- Would the entirety of the Klingon Empire be considered one 'member' of the Federation, or as several?
The members species of the Federation are equal, not the planets they inhabit. The Klingons would be one member of the Federation.
If they join, though, this would be some sort of "friendly takeover". The Federation would saturate the Klingon body of government down to the last colony with their doctrines and officials. They want to make sure, the Klingons do their business by Federation standards.
- Would any colonies that belong to the Empire now be Federation colonies, with their wealth spread among all the Federation members, or would those colonies serve only Qonos and other main Klingon planets?.
The Klingon colonies would most likely not only serve Qonos, as this would be against the Federation ideology. The "wealth" of these colonies will be made available to all Federation entities. However: it is much more likely that these colonies receive Federation development aid. Once technology, social standards and military assets had been proliferated, the Fed Gov't would want these colonies to be able to participate economy-wise fully in the Federation and not just in a Klingon dominion.
- If the Empire conquered a race and gained planets form said race, but destroyed said race in the process, would they still be able to keep those planets, or must they be given up before Federation admittance?
So the Klingons invade 'em before they joined up?
Well, then... it depends on which race and how this affects the whole strategic situation for the Federation and Starfleet.
Good guys: Public outcry, the Klingons will have to give these planets back.
Bad guys: No one will talk about it in public and the Federation (and more so Starfleet!) will see it as a good opportunity to weaken possible enemies and their armed forces. On the other hand: Maybe the media could even model the Klingon invasion as a "just war", though Klingons being Klingons, this would require a few really good Federation spin doctors and a media blockage to cover up atrocities committed by the Klingons. After Klingon admittance, these worlds would be controlled by a Federation (including Klingon) occupation force (and over the centuries we have seen how well occupying forces are received by the occupied and by their own nation's civilians).
- Can individual member planets have their own colonies? If so, can these colonies petition for Federation colony status (opposed to serving only one member)?
I think it depends on the kind of colony. A barren rock in space, barely able to sustain itself, would be allowed to answer to the colonizing nation. If that colony had people on it of non-Klingon origin (which would then be repressed by the Klingons) the Federation would want these people to be free on their own right and maybe join up as well. They would not tolerate a member of the Federation to occupy another race's planet and opress them.
If the colony was on a barren rock in space that had been terraformed to become some sort of entity like a US state nowadays, they would probably remain under semi-Klingon jurisdiction.
Remember: The Feds are totalitarian about this. They would want to have a hand in the gov't of this state as much as they would want participation in the government of Qonos itself.
When I say totalitarion, I do not mean the Federation is a dictatorship. People have civil rights and these are protected and guaranteed. What I mean is, that the Federation is very strict about what they do. In order to maintain such a *huge* democracy certain standards have to exist everywhere in this democracy.
Roddenberry formed the Feds after pre-civil war (1922) "enlightened socialism". Much like what the leaders of the Prague Revolution of 1968 wanted.
Another thought on that matter: If the Klingons would want to sustain their domination of other worlds, they would have to maintain their own armed forces for outside protection and a centralized or decentralized police organisation (being the Klingons, the KADF probably does both).
Now there is only one armed entity in the Federation: Starfleet.
The Klingons would not be allowed to have an own force capable of threating Starfleet, as that would mean, Starfleet had to constantly keep a check on what the Klingon forces inside Federation territory are doing. However: During the war Starfleet probably grew and militarized itself heavily (less "to seek out new civilizations", more "more bang for the buck"), so it could be a welcomed reason to keep the military heads inside Starfleet happy.
Or as Kirk put it: "You cannot trust Klingons."
Looking forward on what other people have in mind on this matter.
EA