Generic Dragon: Help with CR/LA!

[Nifft]

Hey everyone, I'm trying to fix 3.5e's True Dragons. Basically, I want to make a "generic" dragon whose power is separate from its color and alignment -- thus, only a single age table for all types of dragon.

http://www.enworld.org/forums/showthread.php?t=85482

Please help me figure out the CR for these monsters!

Thanks, -- N