I decided to make a mod which allowes you to select the top teams after YDT. If you have any questions, then feel free to ask.
YOUR SAVE FILE WILL BE CORRUPT!
It's recommended that you use Winner's mod which allows you to select all the teams without having to do Day 2.
Winner's mod can be found here: http://www.racedepartment.com/forum/resources/unlock-teams-for-career.788/
Also a HUGE thanks to Ryder for releasing his database editor which will bring many great mods to F1 2013.
Top Teams available after YDT 1.0
A database mod which allows you to access the top teams after YDT.