I love the race, I love the concept, but I don't love the cumulative -6 penalty to stats when you only get a +2, also the movement speed isn't fitting the concept very well, so I'll give a try. This is subject to changes to balance it, I see it balanced as I wrote it, but you know what they say: One does not see its own flaws at first glance.
+2 Dexterity, -2 Strength, -2 Charisma.
Originally Posted by Monster Manual III, p193
Small size. +1 bonus to Armor Class, +1 bonus on attack rolls, +4 bonus on Hide checks, -4 penalty on grapple checks, lifting and carrying limits 3/4 those of Medium characters.
A Warforged scout's base land speed is 30 feet.
Special Qualities: Composite plating, light fortification, living construct traits.
Automatic Languages: Common. Bonus Languages: None.
Favored Class: Scout (if core only: Rogue.)
Composite Plating (Ex): The composite plating used to build warforged scouts provides a +2 armor bonus. This plating is not natural armor and does not stack with other effects that give an armor bonus (other than natural armor). This composite plating occupies the same space on the body as a suit of armor or a robe, and thus a warforged scout cannot wear armor or magic robes. A warforged scout can be enhanced just as armor can be. The creature must be present for the entire time it takes to enchant him.
Composite plating also provides a warforged scout with a 5% arcane spell failure chance, simlar to the penalty for wearing light armor. Any class ability that allows a warforged scout to ignore the arcane spell failure chance for light armor lets ignore this penalty as well.
Light Fortification (Ex): When a critical hit or sneak attack is scored on a warforged scout, there is a 25% chance that the critical hit or sneak attack is negated and damage is rolled normally.
Spoiler: Living Construct Traits.
A living construct possesses the following traits (unless otherwise noted in a creature's entry).
Unlike other constructs, a living construct has a Constitution score. A living construct does not gain BONUS hit points by size but gains (or loses) bonus hit points through a Constitution bonus (or penalty) as with other living creatures.
Unlike other constructs, a living construct does not have low-light vision or darkvision.
Unlike other constructs, a living construct is not immune to mind-influencing effects.
Immunity to poison, sleep effects, paralysis, disease, nausea, fatigue, exhaustion, and energy drain.
A living construct cannot heal damage naturally.
Unlike other constructs, living constructs are subject to critical hits, effects requiring a Fort SAVE, death from massive damage, nonlethal damage, stunning, ability damage, ability drain, and death effects or necromancy effects.
Unlike other constructs, a living construct can use the run action.
Living constructs can be affected by spells that target living creatures as well as by those that target constructs. Damage dealt to a living construct can be healed by a cure light wounds spell or a repair light damage spell, for example, and a living construct is vulnerable to a harm spell. However, spells from the healing subschool provide only half effect to a living construct.
A living construct responds slightly differently from other living creatures when reduced to 0 hit points. A living construct with 0 hit points is disabled, just like a living creature. He can only take a single move action or standard action in each round, but strenuous activity does not risk further injury. When his hit points are less than 0 and greater than -10, a living construct is inert. He is unconscious and helpless, and he cannot perform any actions. However, an inert living construct does not lose additional hit points unless more damage is dealt to him, as with a living creature that is stable.
Can be raised or resurrected.
Does not need to eat, sleep, or breathe, but can still benefit from the effects of consumable spells and magic items such as heroes' feast and potions.
Does not need to sleep, but must rest for 8 hours before preparing spells.