The game is meant to be a REGIONAL game not just one city. A city can only handle one specialization or large item. University, Oil Well, Mining (coal and oar can be together) Omega Co., The Academy. Pick one for your city and do that, then, when that city maxes density city wide, claim a new city that is connected to that one and do a differnt specialization there. Pretty soon all sims have access to all of the special, high worker demand places.
The one exception is with the Academy having researched all Mega Tower Levels, and a fully upgraded City Hall. Then you can max at 8 Mega Towers, splash a bit of residential in the spare holes and, run Omega, Academy and, University together.