Well thank **** you don't own a company then!
I think that is a bit unfair. If this company can do it why shouldn't my theoretical company be allowed to compete on the same level playing field?
Once there is an accident where this type of practice is cited as either a causal or casual factor, you can bet your life the relevant authorities will put a stop to, or severely curtail the practice, so the author might as well take advantage of the situation whilst he still can.
Paying for 300 hours of line training on an A320 does sound rather expensive, but at the end of it I suppose you do have 300 hours of A320 time in your log book? If the company then allows you to carry on working for them without you having to pay them a penny, what a bargain compared to the previous experience of working for them, where you paid handsomely for the privilige. You can always do another job in your free time to make ends meet, or tap up an understanding relative or something. In the meantime the airline only has to pay one salary so everybody is happy. What could possibly be wrong with that?
The only other question I have is what happens at the point the airline has to start paying you as a salaried First Officer under the terms of its guarantee? Perhaps I am being sceptical, but won't they be slightly more interested in the new people who will be paying them hard cash for line training, and the "graduates" who will then work for free? Why would you need to start paying a salary? Unless they promise to stop this practice after a certain number of people have signed up, or the pyramid can only get bigger?
I think I would want to run this "guarantee" through a lawyer myself, if I was relying on it for any meaningful purpose.