I believe what he is trying to say is that, simply, he wishes that one would be able to select the UCD, and buy all 30 cars at once.
The way that the UCD is set up currently, you can only buy one car at a time, and once you purchase it, you must wait for the game to auto save and also wait for the slow menus to return you to the main GT Life screen.
What he's saying is that he wishes there was a tool to select all 30 cars at once and buy them simultaneously, as opposed to buying one, waiting for the game to auto save and redirect him to the main menu, and then have to repeat this process 29 more times to acquire all 30 cars in the UCD.
Hopefully this makes sense, I don't see how he (or I) could make it much clearer.