Ok, since this lost its motivation I'll just post how I would handle the two extra uniques per civ. Unlike the rest of the people in this thread I don't think adding a unique improvement per civ would be a good idea, unique improvements are already losing their uniqueness with CPP, there is a limit to how many unique ideas for improvements you can have.
I'm also not going to touch on about half the civs, mostly because I don't know enough about them to make a solid suggestion. I mean seriously, who knows anything about Assyria anyways?

. I'm also not going to read or refer to the existing 3UC or 4UC mod. They are probably great mods, but we've already changed to base balance and some unique in CPP so we are going to have to do most of this from scratch anyways (with the exception of maybe names and art).
I'm going to try and stay with one extra unique unit and one extra unique non-unit per civ, if only to have some consistency.
American
UU: A marine replacement.
UB: A Mall UB would be a pretty fun idea but I'm not sure what it would replace.
A Factory replacement could work, but I'm not a fan of giving America more lategame things. It gets kinda hard considering the US doesn't really have a long history.
Arabian
UU: Drawing a blank here, a horseunit would be an easy solution, but placing two unique horse-units in the same civ is kinda lame. A replacement Great general or Prophet could work aswell.
UB: Madrasa unique library. Something complementing Arabia's desert-theme could also work.
Assyrian
Blank
Austrian
Honestly, I know what firaxis tried doing here, but the Austrian empire was not historically relevant and lasted for 60 years.
For a UU, those hilltroops from communitas would be cool.
Aztec
A unique temple would probably be the best approach, not necessarily faithbased.
For a UU it gets rather hard, you have to make a decision if you want a unit that upgrades from the Jaguar or not.
Babylonian
UB: A Ziggurat
UU: Probably some kinda melee unit.
Brazilian
No clue. Football stadium?
Byzantine
For a UU maybe a dromon replacement? Some kind of defensive unit could make sense aswell.
UB: Probably a hippodrome replacing a colosseum (Yes I'm aware that it wasn't a hippodrome, it was The hippodrome, but the colosseum is equally bad)
Carthaginian
UU: Bring back the Elephant I guess.
UB: Cothon replacement for a lighthouse.
Celtic
UU: Swordsman or archeryunit probably, I would suggest something not sharing upgradepath with the pictish warrior.
UB: Some religious building or possibly the Dun wall replacement from civ4.
Chinese
UU: A footsoldier for sure, what to replace and what to name it however I'm leaving to you.
UB: Bringing back the papermaker could work, some military or cultural building could also work.
Danish
UU: Longboat, trireme replacement.
UB: Stave church?
Dutch
UU: Some unique great person?
UB: A harbor would work, a bank could also work, so could some caravansary replacement. Should be something tradebased anyways.
Egyptian
UU: No idea. Replacement worker as slave-labor might be a bit harsh.
UB: I dislike monument replacements completely, but this feels like a decent place for one.
English
UU: Bring the longbow back? Some kind of longswords or swordsman replacement could also work if one finds the longbow way too cheesy.
UB: A harbor, a bank, a seaport, a stable could all work. I'd suggest something tradebased as the English really only are military based at this point.
Ethiopian
No idea.
French
UU: A heavy mounted unit would be a pretty good fit imho.
UB: A castle would feel kinda defensive coupled with their defensive UI. A Salon like the one from civ4 would be fun, as would something culturebased.
German
UU: A foot-soldier or a artillery replacement would be kinda fun. A pike-man replacement could also work, if one wants to take a step that way.
UB: Someone from Germany could probably figure something way better out.
Greek
UU: I'd probably give them their horseunit back.
UB: No idea.
Hunnic
Incan
No
Indian
UU: Not really
UB: Either bring back the mogul fort or give them something cool like the mausoleum of civ4.
Indonesian
UU: A ranged boat would work fine here probably.
UI: I'd suggest a plantation-replacement actually. This is the one civ you can guarantee to always have plantation-resources, so why not go for that?
Iroquois
UU: Nah
UB: I would probably break the forest-theme at this point, you don't want to much affecting one tiletype or you're going to run into trouble.
Japanese
UU: No clue really, a boat would fit well, but the Japanese were notoriously bad shipbuilders.
UB: Probably something that breaks the military focus, maybe a cultural or science building?
Korean
UU: Bring back the turtleship
UB: At this point I'm not really sure. They need a building that doesn't help their science at all, but I have no clue what that would be.
Mayan
UU: Holkan spearman?
UB: Ceremonial Ball Court, Colosseum replacement?
Mongolian
UU: Keshik!
UB: Something clever.
Moroccan
UU: No clue.
UB: They do need some kind of building. Probably nothing defensive as they already have that covered.
Ottoman
UU: Why not bring the Sipah back?
UB: Hamman, Turkish bath, there are a lot of alternatives here.
Persian
UB: No clue, the Persians had skilled riders, but I don't know if they had a specific name.
UB: Civ4 had some kind of apothecary replacing a grocer, we could do that.
Polish
Polynesian
Better if someone who actually knows what they're talking about take it from here.
Portuguese
UU: Probably not another boat, but I'm not really sure what kind of landbased units they used.
UB: A harbor? A lighthouse could work aswell, as could a seaport.
Roman
UU: What's there to say? Bring back the Balista.
UB: A Forum, Market replacement for sure.
Russian
UU: I'd love to place something earlier here, but no clue what that would be.
UB: Bring back the Krepost. Do a major rework on its abilities, but the building itself is solid.
Shoshone
UU: Bring back the Comanche riders.
UB: No clue.
Siamese
Nope
Songhai
UU: Nope
UB: The mud-pyramid mosque with some unique effects for fun could be nice.
Spanish
UU: Their unique unit from the base-game was pretty fun, Terecio or whatever it was called.
UB: This is hard, I'd probably make it a UI, but I'm not sure about that either.
Swedish
UU: Either bring back the hakkapeliitta or give them a unique Cannon replacement.
UB: Not sure.
Venetian
UU: Bringing back the great galleass is a no-brainer.
UB: Maybe that unique courthouse someone kept mentioning earlier?
Zulu
F Shaka.