Eh, that is highly disputable. Given that it was granted a monopoly, how does it differ from a state, except that it is privately owned? Seems like a monarchy of sorts, not so much a private agent. Firms that are contracted by governments or other firms are a better bet, but even here government’s recklesness and stupidity render it a bad idea to mention these firms as good examples of private armies, especially in the case of firms like Blackwater, which is essentially a private arm of the state.
Has it ever occured to you that all private armies where always employed to attack rather than to defend? I am not aware about a single event, where a considerable force was hired to defend rather than to attack. Even the famous Swiss forces where hired for this use. They for sure defended their territories without payments.
Now, what reason might a free society have to attack, that is plan a war rather than plan a defense? Civil disobedience is a great, maybe the most effective way, to fight against an enemy, see Ghandi for that matter - not what happend later though-. And for a immediate attack on a free society a militia is also worth considering. I know there is no way to fight against nuclear weapons or to win a fight against a modern army anyway, unless you employ the way people do in Afganistan for example (This does not mean they do it for moral reasons). If anyone is a fighter ready to attack any foreigen attacker than any aggressing force has a hard time to get control over any territory, not to speak over the people - Have a look at Iraq-. If a “green zone” is all the biggest military machine on earth is able to achieve after years of war and trillions of dollars spend, that should give you an idea about how effective insurgence and small group fighting is.
If it were true that free people will not voluntarily risk their lives to defend their freedoms, then we would not have won the American Revolution or the War of 1812.
With regards to the East India Company, the early East India company was a genuine trading corporation that did not initially aspire to rule the subcontinent but comprised a few dozen trading posts scattered along the Indian coast where it traded for opium, tea and Indian textiles to be sent back to Europe. These trading posts had to make their own private arrangements for protecting themselves against local bandits and warlords and so paid for their security from local mercenaries out of their own pockets.
Of course as it grew in size and power it became a de facto state, levying taxes and establishing a monopoly on Opium, but we shouldn’t forget its anarchic origins.