So, when you are going to buy a vehicle, you'll probably know what the name of the vehicle is. And I dont know if you are aware of this, but if you press on the top of the list, it'll arrange the name of the cars in alphabetical order (a-z) and if you press again it'll arrange it in the opposite manner (z-a). So if you wanna search for a vehicle, like say for an example, Elegy, you can find it in the part where vehicle names starting with 'E' are arranged. So in my opinion, the current system works pretty fine and is efficient enough. So I am sorry but I am voting Negative.
Most of the GUIs nowadays has been updated with search bars even if the command /search Name has been existing for many years. Well most of the players doesn't even know that command so adding search bar to other GUIs that doesn't have one should work perfectly fine. It is also easier when you're looking for a particular vehicle.