I'd like to add a second part to this request. I have another idea regarding differentiation: personnel salaries. I'm running a small prop airline out of LUX as a test airline, and I found out that you have limited choice regarding personnel salaries. Even if you only slightly decrease their salaries, your company image and morale will drop so significantly that I can understand that most people refrain from this option. However, a regional pilot earning $4400 a month on a DHC-8 out of LUX is simply not realistic (even KLM E190 First Officers don't earn that much in their early stages of employment).
This is just one example of many cases, and so I thought of the following: why not let us choose the salaries at the start of the game? If you don't decrease the salaries in the first place, your morale and image won't drop as well. Of course, if you operate under lower salaries you'll mostly have less qualified personnel. This could then lead to more flight delays, less accurate demand estimates and a slower increase in company image (as, for example, marketing is less successful), just to name a few.