No, 150 amp panels are available.
They are not popular.
They are cheaper than 200 amp panels.
2/0 should handle 200 amps.
Power companies specify the size of wire to be used with your electrical service here. Kentucky Utilities, for example, specifies a 2" mast with 2/0 for residential. For commercial, you can still use 2/0, but you have to use a 2 1/2" mast. Your area may have other requirements that I know nothing about.
If I were you, I'd find another electrician to talk to. Check with a local electrical supply house. Dealers often have someone with a good knowledge of what is being used in the area. They can recommend knowledgable electricians to you, to figure out what you want to do.
The code varies area to area because the code is subject to the inspector's interpretation. That's the part of the code that gave me gray hair and stress lines, and half of why I don't don't do electrical work anymore.