Well that's a much different point that what you originally posted. I don't really disagree; they're employees of the UFC, so if the brass suggests a fight, they should take it, barring injuries. However, a ranking system is really the best way to go about it, because it gives the lower-ranked guys a well-defined plan for getting to the top, as opposed to some sort of patronage system where whoever the flavor of the week is gets a shot because he's marketable or what have you.* Just randomly picking people seems arbitrary and would probably discourage a lot of less charismatic yet talented fighters from even trying.
* not aimed towards any fighters in particular :icon_chee