You forgot one example, working together with others in order to complete a task.
Buying materials or grinding all the scripts required are not the only options, just like how FC crafting requires multiple people present and best approached by working together to share the burden of gathering all the materials to craft things like airships etc. The specialist system is here to stay and as someone else pointed out it would not just be the rich buying the materials, you could potentially get rich from selling your own then using that gil to purchase what you cannot craft yourself.
Another point is even very few omni-crafters could craft everything themselves prior to these scripts, people who had capped all the crafting classes levels, gear and all master books etc were a tiny minority or the playerbase. I find it ironic that people are whining about the few supposedly rich people/FC's that might get a head start by spending their gil that they probably had to work hard to get more than you...yet don't see people here applying that same logic to the few people who worked hard to level and cap, gear and gain master books which have them the same advantage over others. The only real difference between the two is one worked hard to gain gil the other worked hard to level, gear and obtain books...both however comprise of the few having a slight advantage over the majority of others.
People in here are being hypocrites in their efforts to craft a flawed excuse against red scripts. There are legitimate issues with red scripts such as the low cap and high price of materials but this argument against people buying materials because through their hard work are rich enough to do so not one of them. Especially since it is not only hypocritical to take that stance but also ignores the fact you could become rich yourself selling to them and then buying any you cannot craft yourself with that gil.