After reading all this I went and looked at the rules from Paizo. Briefly here is what I used;
http://paizo.com/pathfinderRPG/prd/monsters/monsterCreation.html
Core Rules p. 82 & 83 quote - " A familiar is an animal chosen by a spellcaster to aid him in his study of magic. It retains the appearance, Hit Dice, base attack bonus, base save bonuses, skills, and feats of the normal animal it once was, but is now a magical beast for the purpose of effects that depend on its type. Only a normal, unmodified animal may become a familiar."
Familiar Basics: Use the basic statistics for a creature of the familiar’s kind as described in the Pathfinder RPG Bestiary, but with the following changes.
Hit Dice: For HD use the char level or the familiar’s normal HD whichever is higher.
Hit Points: Familiar has half the char's regardless of actual HD
Attacks: Char's BAB as calculated from all his classes. Use the familiar’s Dex or
Str mod whichever is greater, to calculate the familiar’s melee attack bonus with natural weapons.
Damage equals that of a normal creature of the familiar’s kind.
Saving Throws: For each saving throw, use either the
familiar’s base save bonus (Fortitude +2, Reflex +2, Will
+0) or the master’s (as calculated from all his classes),
whichever is better.
Skills: each skill in which either the char or the familiar has ranks, use either the normal skill ranks for an animal of that type or the char’s skill ranks, whichever is better. regardless, the familiar uses its own ability modifiers. Familiars treat Acrobatics, Climb, Fly, Perception, Stealth, and Swim as class skills.
Minimum at 1st level the familar will get the following;
1st- 2nd +1 Natural Armor , Intelligence 6 - awarding 2 Skill points
FEATS: Alertness, improved evasion, share spells, empathic link
+2 Initiative Bonus
+2 Fort, +2 Reflex +0 Will Saves
Assumptions:
1. Large is equivalent to Giant
2. the difference between Large and giant scorpion template is +1 Str, +6 Dex, +2 Con
Applying all this I get using the monster creation template in conjunction with the giant scorpion template and extrapolating;
Greensting Scorpion CR 1/4
XP 100
N Tiny vermin {Augmented}
Init +5; Senses darkvision 30 ft., tremorsense 30 ft.; Perception +4
DEFENSE
AC [18] = 10 + 5 (dex) +1 (Natural) +2 (Size)
Touch: [17] Flat-Footed [13]
hp 4.5 (5) (1d8+0 ) <--- Use 1/2 Characters HP round down
Fort +4, Ref +2, Will +0 <--- May use Character Saves
Immune mind-affecting effects
OFFENSE
Speed 40 ft.
Melee 2 claws 1d2 +1 (plus grab) , sting 1 +2 (1 plus poison)
Space variable (1/2 to 2 1/2 ft.); Reach 0 ft.
Special Attacks constrict (1d2)
STATISTICS
Str 3, Dex 20, Con 10, Int [6], Wis 10, Cha 2
Base Atk +1; <--- Use Characters BAB
CMB [-5] = 1 (BAB) + -4 (str) -2 (Size) <-- Adj. By Char BAB
[-1] Grappling (+4 Grapple)
CMD [9] = 1 (BAB) + -4 (str) +2 (size) + 10 <--- Adj. By Char BAB
[13] vs. Trip
Skills Climb +2,
Perception +4,
Stealth +4;
Racial Modifiers +4 Climb, +4 Perception, +4 Stealth
SPECIAL ABILITIES
Poison (Ex): Sting-injury; save Fort DC 12; frequency 1/round for 6 rounds; effect 1 Strength damage; cure 1 save. The save DC is Constitutuion-based and includes a +2 racial bonus.
FEAT:
Improved Natural AC (1)
Environment: warm or temperate deserts, forests, plains, or underground
Organization: solitary
Treasure: none
Okay, having done all that, the familiar will level as the character does which will progress the abilities by HD increase. Off-hand not a bad scale down attempt I think. Thoughts?
Regards,
-DogBoy