-The Terrans don't start with any market or entertainment building? Why don't they have traditional entertainment and market economies?
It's not only the Terrans. None of the races have those techs. I somehow missed that while going through the files.
-The Arceans and Thalans both have techs called xeno anthropology, but they do different things.
Those are two different techs. For the Arceans, it's just a renamed Xeno Business, while for the Thalan, it's a unique tech.
P.S. Is there a way to set up a game, and just watch the A.I. control all the teams, without having to actually play? Like an observer mode?
Yes, but it takes a little work, and isn't necessarily stable.
Create a link to the GC2TwilightOfTheArnor.exe, then right-click on it and choose properties. You need to add "cheat" (without the quotation-marks) to the end of the Target field. It should look similar to this: "x\Stardock Games\Galactic Civilizations II - Ultimate Edition\Twilight\GC2TwilightOfTheArnor.exe" cheat. The actual path depends on where you installed the game, and what version you are using (the Steam-path, for example, will probably look quite different).
Once done, start a new game and press CTRL+Z. This will put the AI in control of your race. You can then either end the turn or press CTRL+N. Ending the turn will mean that the AI is probably loosing a turn and is influenced by your decisions (what tech you chose at the start of the game, for example), while starting a new game by pressing CTRL+N means, that the AI is already in control from the get go. I usually use the latter, just to be sure. You will also need to use CTRL+U to unveil the map. Otherwise, you won't be able to see what is going on. Pressing CTRL+Z again will put you back in control, but that may not always be possible.
At some point during auto-play, usually when war brakes out, the game will go into what I call "hyper-mode". The screen will start to flicker and notifications will appear, even if you disabled them. Cheats don't work while this is happening, and the only clues you have on what is going on comes from the short glimpses at the notifications. Hyper-mode usually ends when one of the races gets wiped out, but not always. Sometimes it won't end, even though only one race remains. The only way to stop it then is to quit the game by pressing ALT+F4. There is also the possibility of the game crashing during auto-play, but I haven't had that happen in quit a while.
A quicker method of setting auto-play up are the "quicktest" and "aitest" commands. "quicktest" automatically starts a new game, using the last used settings (although it will often set Asteroids to Rare), while "aitest" puts the AI in command from the start. However, you still need the "cheat" command to be able to use CTRL+Z and CTRL+U. This method also has the same problem as the first one, so it doesn't matter which one you use.
Kind of an out there idea, but is there a way to make a political party have a war profiteering bonus?
It's possible (War Profiteering has the ability-number 36), but I'm not sure, if that would be a good idea. War Profiteering is one of the most powerful abilities, so having it from the start could be quite unbalancing.