This game can be salvaged, for sure.
Most of the core ideas are good, just overly simple in their current implementation. Like, global happiness. This concept can work. But right now it's kind of like borderline personality disorder: all or nothing. It needs - and crucially,
can handle - more complexity. Hopefully being a traffic cop for growth is just the beginning.
There's tons of room to add things, if the AI can be taught how to use the new stuff. Some of the existing things (national wonders, for instance) are looking better after some tweaking. Maybe a really good game will start to emerge, once we get out of beta.
But anyway, I guess you were asking for specific ideas. Things I would focus on if I were a designer:
Tile improvements: there is nothing a worker can do to help a city get more hammers if it lacks hills. We need a tile improvement that trades food for hammers, like the workshop in Civ4. And beyond that, more choices generally would be a good thing. The selection is too limited, and a bit boring.
Buildings: reward smaller/builder empires with buildings that more substantially improve the overall productivity of each citizen. Look at each existing building, and think about what tile yield it might improve, or which specialist it might boost.
AI: still needs work. In my current game I'm still seeing things like unimproved luxury tiles, and pillaged tiles not getting priority. Sid said in that keynote speech that he's never gotten mail from players saying they won too easily. Consider this to be my letter. I used to play on Noble/Prince in Civ4. In Civ5 I'm up to Emperor already. The game should be kicking my butt, what gives?!
...do those three things, and maybe Civ5 becomes a worthy successor to the series.
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