I do agree with your point on Underground Nukes. They're either devastating to use (and awful to get hit with), or kind of worthless. Tough to balance this I imagine.
I disagree with your point on the AI, but Ive only ever gone up to Executive (my usual level for SP games). They play very smartly, scrapping facilities well, turning off mines when power is expensive etc, also they play a much more reserved game as far as expansion goes, its slower but lets them get much earlier stock purchasing. They use the Black Market way more than human players which can be annoying since prices are often quite high, but as far as them singling out the human player goes I have to disagree with you, they tend to focus the top stock values. If that happens to be you, yea youre gonna hit, but good luck having a high stock price early against that level of AI, not going to happen often 
Campaign needs work but Soren just made a video about it acknowledging this and talking about future plans, so that Im not too worried about.
Ive found Debt to be much more of a factor in MP games than SP. This might be a bit due to how new the game is though, a lot of people in MP acrue insane amounts of debt getting stuff in auctions, without realizing how vulnerable it makes them (I saw someone's stock hit $.98 the other day thanks to their insane debt from auctions!!). People tend to also rush Upgrading their base, which can also make them vulnerable to rising prices in Life Support and Power, as well as over-inflate the price of glass, letting someone like me with a more controlled approach to expansion sell a bunch of highly priced goods and get more claims on the black market, making me much stronger in the long term.
One thing I'd really like to start seeing more support for is MP team games. Atm, there is no way to team chat, and setting up a lobby for this game type can also be troublesome. For example, if I wanted to have my friend and I play against 2AI players, I still have to make the lobby for 4 players, and later there is no way to make the lobby private, so even if I have my friend, myself, and 2 AI players set up and ready to go, other people can still join my lobby as it doesn't count the AI players as part of the 4/4.
Anyway, hope to see you in some MP games sometime, its quite fun! 