Unresolved

drivers with full attributes

You can't. A driver with all attributes at 20 will be a minimum of Level 18 and your team is L15. The game will not permit you to hire drivers or staff who have a higher level than your team. 
The best thing to do is either take a Talent 20 driver from your academy or buy one from the market/other manager and train them up to 20 in the remaining attributes. Note that the experience attribute can't be trained, to get this to 20 the driver will have to compete in races.