Besides your age problem, it might be an attitude problem. What makes you think that as a CFI you will only deal with people who don't want to learn? The reason airlines like to hire CFIs is because they probably have to ability to deal with and relate to people with varying levels of experience and expertise.
Heres another thought: the reason many airlines have minimum age requirements is because they want a certain level of maturity. On top of that, unless you have previous experience as a "professional aviator" most airlines are going to be wary about investing time and money in you before you have proven your ability as a professional. Yes, there are exceptions to this rule but they are just that, exceptions. To sum up, my advice would be to shelve your attitude, get your CFI ratings, teach, scare yourself a few times, learn a few things about what it means to be a professional, have some fun and THEN start thinking about the airlines. Besides, a 19 year old kid wouldn't be that much fun on the overnights anyway unless you're in Canada
PS
4 years in the right seat at Colgan or Great Mistakes would blow giant donkey balls.