OP said:
Quadrupedal Movement (1 RP): Green men can use their middle set of limbs as arms or legs. When quadrupedal, his speed increases by +10 feet but his reach is reduced to 5 feet. He must have nothing in his hands to use quadrupedal movement.
As for the Semi-Quadruped issue, the ability to switch between biped and quadruped at will means that the disadvantages for a Multi-Armed creature are minimal, because it will be in whatever stance is most beneficial at the time.
What I see from this is that the Green Man can choose to have the advantages of a quadruped (with +10 feet speed), or the advantages of not being a quadruped (extra hands, reach). That cannot reasonably be worth less than the cost of being a quadruped (2 points according to Centaurs) and could be worth more. As Cleon points out, there are few times when one would use both advantages fully. For 2 point, I would say keep it as it is, but it takes the Green Man a full round action to stretch out from Quadruped to Biped, or vice versa. If he can swap as a standard action, 3 RP, and if he can switch faster than that, 4 RP. Or just remove that ability entirely, given that:
The very first description of Green Martians in A Princess of Mars, Chapter III: My Advent on Mars describes them as being able to move on all fours. Five or six had already hatched and the grotesque caricatures which sat blinking in the sunlight were enough to cause me to doubt my sanity. They seemed mostly head, with little scrawny bodies, long necks and six legs, or, as I afterward learned, two legs and two arms, with an intermediary pair of limbs which could be used at will either as arms or legs. Their eyes were set at the extreme sides of their heads a trifle above the center and protruded in such a manner that they could be directed either forward or back and also independently of each other, thus permitting this queer animal to look in any direction, or in two directions at once, without the necessity of turning the head.
Offhand I can't recall any descriptions of the Green Martians running on all fours - but then they usually jump on a Thoat whenever they want to get anywhere in a hurry.
The books do say their limbs are articulated in the same fashion as a White Ape, and if I remember correctly there are several references to White Apes running on four legs.
If the only time we see the use of the extra arms as legs is as newly hatched babies, it doesn’t seem they gain any great advantage from using the "intermediary limbs" as a second pair of legs. Why do they never take advantage of this as adults? Maybe they derive no game-mechanical benefits for doing so. Maybe they lose some flexibility in growth to adulthood and can’t effectively use their middle limbs as a second set of legs. Maybe it just takes too long to switch modes as joints twist and get stiff from one configuration. Regardless, it doesn’t seem four legged movement is a hallmark of the race. Maybe some unusual Green Men can still switch between orientations, taking "Semi-Quadruped" as a feat, but if that is its only appearance in the source material, it hardly seems necessary as a racial trait.
What do humans look like under this model, by the way, since they are considerably stronger? Is this intended for a Mars campaign, so other standard races aren't represented, or do they also get STR boosts consistent with the fact we're giving a "weaker than human" source material race a STR bonus compared to humans? It seems a lot easier to keep Human as the baseline, and not provide this race a +4 STR bonus plus large size. I'm not sure why they get CHA dropped - they made friends with John Carter easily enough. Seems like a race custom designed for warriors. I'd expect Barbarians and Monks to gravitate to this as written.
Why Monks? Well, they don't have to drop and retrieve weapons to shift between biped and quadruped. CON and STR bonuses are nice and CHA isn't their strong suit anyway. Now, how does Flurry of Blows work for a guy with 4 arms?
