Help w/trait to delay 1st level feat acquisition

[Jim.DiGriz]

I'm trying to create a trait that allows a character to delay taking his 1st level feat until he reaches 2nd level. This would allow 3/4 and 1/2 BAB classes to pick up feats requiring a +1 BAB, which I think is worth the cost of a trait for melee-oriented clerics and rogues (and which would be a bit cheesy to simply allow at no cost, IMO).

Can anyone tell me how to accomplish this? I realize I could just create a trait with the appropriate description and tell the player to live with the validation error until 2nd level but I'd rather make it fully functional if possible.