Level of dragon
I got the impression it was easy to modify monsters based on the standard stats, etc.
Can't you make a level 12 white dragon level 16 by adding +2 to all of its ability modifiers? I mean, everything so far is based on base abilities and those scale by level. After that you're maybe adding a few hit points.
So the level 3 white dragon at level 6 would be something like:
Large White Dragon (Young)
Level 6 Solo Brute
Large Natural Magical Beast(Cold, Dragon)
AC 22
FORT 22
REF 20
WILL 21
HP 180/90 (Not sure on the HP mod off the top of my head)
INIT +3 SPD 6 FLY 6 (Hv)
Sense Preception +9;darkvision
Resist 15 cold; save +5
Attacks:
m Bite Reach 2; +8 vs AC; 1d8+6+1d6 cold
M Claw Reach 2; +8 vs AC; 1d8+6
M Double Attack Standard; 2 claw atks; if hits M or smaller with both, free basic melee atk against same target.
Coldsnap Opp atk that hits deals +1d6 cold.
Limited Powers
Action Points 2
Frightful Presence Burst 5; +6 vs Will; stunned 1 rd. Aftereffect -2 atk (save ends).
Breath Wpn Rchg 5. Blast 5; +6 vs Ref; 3d6+6 cold AND slowed AND weakened (save ends both)
Bloodied Breath Reaction, when first bloodied; breath wpn.
Abilities: Ice Walk, Overland Flight 10
Skills: Athletics +17
STR +7 (18) CON +7 (18) DEX +3 (10) INT +3 (10) WIS +4 (12) CHA +2 (8)