RE: It's really just a contract.
Yes, that's it!
It's a contract that creates a legal fiction and access to benefits available to the created legal fiction.
The legal fiction created by the contract with the govenment is the core/central component of the contract.
Without the legal(access to government benefits) fiction, the contract is not a corporation.
RE: contracts are very libertarian
Agreed. ( note: corporations are contracts made with the government )
RE: The forming of a corporation might be a bit more complicated, but absent government and the whatever special benefits that governments decide to give corporations, a corporation is just an elaborate contract for collaboration of resources and efforts.
Absent government (and government benefits) there is NO NEED for a legal(government created) fiction called a corporation.
And there is no requirement that there be any collaboration(internal to the corporation) though corporations MAY collaborate internally(separate policy/contract) IF DESIRED.
NOTE: People can ALSO contract to collaborate resources and efforts WITHOUT a corporation.
Now then . . . the CONTRACT with the government to form the corporation includes not only benefits, but responsibilities . . . including the responsibility to pay the proper taxes to the government. TA DAH . . . NEW FIRE STATION