Yes, I think I'd agree to your simple CR (ie, + base construct's CR).
So shall I update it with "Equals the sum of the base creature's challenge rating plus the base construct's challenge rating. The standard base construct challenge ratings are CR W for stone, CR X for wicker, CR Y for winged, and CR Z for wooden."?
Are you OK with the "
Level Adjustment: See Pilot Advancement?" proposal?
The original is 5d10. That's an odd damage number in 3.X, but what if we do 2d6, 1d10, 2d8, 2d10, 3d8? Or just 1d10 to 5d10?
Since we're putting the damage in a lookup table it doesn't seem to matter so much if it's a non-standard progression. We don't have to worry about some smart alec trying to use Improved Natural Attack on it, since it's a Trample special attack rather than a natural weapon.
Come to think of it, that points out a minor error in the current draft: The table in question should no be named "Guardian Juggernaut
Natural Attack Table", but just "Guardian Juggernaut
Attack Table".
I guess it could be "Guardian Juggernaut Damage Table", but I like "Attack" better.
For the damage, the original creature's Stomp attack does roughly twice the damage of a stone juggernaut's slam attack (5d10 averages to 27.5, a stone juggernaut's fist does 3d6+1d2+Str bonus, or 12+Str bonus). Since we're giving the creature two slams, I reckon we should set the damage to roughly the same proportion.
Dang it, we should include Strength in the Stomp special attack's damage. I propose a modification to "If the victim fails a Reflex save, the opponent takes bludgeoning damage as listed in the "Stomp" column of the Guardian Juggernaut Natural Attacks Table
plus 1½ times [or 2 times?] the juggernaut's Strength bonus, following which the juggernaut may either pin or kick the opponent."
While we're at it, I fancy reducing the size cap of the Stomp to allow Large juggernauts to use the attack.
So, how about we use a "1½ times Strength bonus" and set the damage to:
Large: 2d10
Huge: 4d8
Gargantuan: 6d8
Colossal: 8d8