Given the way the 4th ed system handles ranks I don't think it is wise to link skills to RP like the BRCS did. That system worked well for the 3.5 system - but doesn't translate well into 4th ed.

I would instead go back to linking them to classes like 2nd ed did.

And yes, I too would go back to the 2nd ed source if I was making a 4th ed BR system.