I went scanning around, looking for any precedence for making more than one grapple successful grapple attempt per round, or other feats/abilities pertaining to grappling.
Improved Grab (from SRD) - Can use one part of body (on successful attack) to grapple and hold a smaller opponent with just that part of the body, hereby allowing the creature itself to not be considered grappled, and using its remaining attacks to grapple additional opponents. It is unclear if the attacker could make their successive attacks with the specific body part performing the hold. See bold and italic emphasis.
Improved Grab (Ex): If a creature with this special attack hits with a melee weapon (usually a claw or bite attack), it deals normal damage and attempts to start a grapple as a free action without provoking an attack of opportunity. No initial touch attack is required. Unless otherwise noted, improved grab works only against opponents at least one size category smaller than the creature. The creature has the option to conduct the grapple normally, or simply use the part of its body it used in the improved grab to hold the opponent. If it chooses to do the latter, it takes a –20 penalty on grapple checks, but is not considered grappled itself; the creature does not lose its Dexterity bonus to AC, still threatens an area, and can use its remaining attacks against other opponents. A successful hold does not deal any extra damage unless the creature also has the constrict special attack. If the creature does not constrict, each successful grapple check it makes during successive rounds automatically deals the damage indicated for the attack that established the hold. Otherwise, it deals constriction damage as well (the amount is given in the creature’s descriptive text). When a creature gets a hold after an improved grab attack, it pulls the opponent into its space. This act does not provoke attacks of opportunity. It can even move (possibly carrying away the opponent), provided it can drag the opponent’s weight.
Swallow Whole (from SRD)
Swallow Whole (Ex): If a creature with this special attack begins its turn with an opponent held in its mouth (see Improved Grab), it can attempt a new grapple check (as though attempting to pin the opponent). If it succeeds, it swallows its prey, and the opponent takes bite damage. Unless otherwise noted, the opponent can be up to one size category smaller than the swallowing creature. Being swallowed has various consequences, depending on the creature doing the swallowing. A swallowed creature is considered to be grappled, while the creature that did the swallowing is not. A swallowed creature can try to cut its way free with any light slashing or piercing weapon (the amount of cutting damage required to get free is noted in the creature description), or it can just try to escape the grapple. The Armor Class of the interior of a creature that swallows whole is normally 10 + 1/2 its natural armor bonus, with no modifiers for size or Dexterity. If the swallowed creature escapes the grapple, success puts it back in the attacker’s mouth, where it may be bitten or swallowed again.
Snatch Feat (from SRD) - Believe on successful attacks, you can grapple someone, drop them as a free action, grapple someone on next attack, drop as free action, etc. to perform multiple grapples a round, though ultimately end up with only 1 enemy grappled. If the improved grab special attack allows successive attacks with the body part holding the enemy, this might allow snatches of more than 1 creature at a time (2 successful attacks with same natural weapon on different enemies).
SNATCH [GENERAL]
Prerequisite: Size Huge or larger.
Benefits: The creature can choose to start a grapple when it hits with a claw or bite attack, as though it had the improved grab special attack. If the creature gets a hold on a creature three or more sizes smaller, it squeezes each round for automatic bite or claw damage. A snatched opponent held in the creature’s mouth is not allowed a Reflex save against the creature’s breath weapon, if it has one.
The creature can drop a creature it has snatched as a free action or use a standard action to fling it aside. A flung creature travels 1d6 x 10 feet, and takes 1d6 points of damage per 10 feet traveled. If the creature flings a snatched opponent while flying, the opponent takes this amount or falling damage, whichever is greater.
Big 'Object' vs little creature Multiple target grapple attempts!
ANIMATED OBJECT in MM/SRD:
Constrict (Ex): A flexible animated object such as a rope, vine, or rug deals damage equal to its slam damage value plus 1- 1/2 times its Strength bonus with a successful grapple check against a creature up to one size larger than itself.
An object of at least Large size can make constriction attacks against multiple creatures at once, if they all are at least two sizes smaller than the object and can fit under it.
Grapple, swallow, cleave, grapple.
BEHIR in MM/SRD:
Swallow Whole (Ex): A behir can try to swallow a grabbed Medium or smaller opponent by making a successful grapple check.
A behir that swallows an opponent can use its Cleave feat to bite and grab another opponent.
A swallowed creature takes 2d8+8 points of bludgeoning damage and 8 points of acid damage per round from the behir’s gizzard. A swallowed creature can cut its way out by using a light slashing or piercing weapon to deal 25 points of damage to the gizzard (AC 15). Once the creature exits, muscular action closes the hole; another swallowed opponent must cut its own way out.
Big flying creature crushes smaller creatures and can pin/grapple all beneath.
Dragon in MM/SRD:
Crush (Ex): This special attack allows a flying or jumping dragon of at least Huge size to land on opponents as a standard action, using its whole body to crush them. Crush attacks are effective only against opponents three or more size categories smaller than the dragon (though it can attempt normal overrun or grapple attacks against larger opponents).
A crush attack affects as many creatures as can fit under the dragon’s body. Creatures in the affected area must succeed on a Reflex save (DC equal to that of the dragon’s breath weapon) or be pinned, automatically taking bludgeoning damage during the next round unless the dragon moves off them. If the dragon chooses to maintain the pin, treat it as a normal grapple attack. Pinned opponents take damage from the crush each round if they don’t escape.
A crush attack deals the indicated damage plus 1-1/2 times the dragon’s Strength bonus (round down)
Gelatinous Cube (SRD) can engulf (considered grappled once engulfed) as many large or smaller enemies it can move over in a round
Gelatinous Cube in SRD:
Engulf (Ex): Although it moves slowly, a gelatinous cube can simply mow down Large or smaller creatures as a standard action. It cannot make a slam attack during a round in which it engulfs. The gelatinous cube merely has to move over the opponents, affecting as many as it can cover. Opponents can make opportunity attacks against the cube, but if they do so they are not entitled to a saving throw. Those who do not attempt attacks of opportunity must succeed on a DC 13 Reflex save or be engulfed; on a success, they are pushed back or aside (opponent’s choice) as the cube moves forward. Engulfed creatures are subject to the cube’s paralysis and acid, and are considered to be grappled and trapped within its body. The save DC is Strength-based and includes a +1 racial bonus.
Tendriculos (SRD) gives a good example of improved grab, combined with a nifty free action to transfer it to mouth with auto-damage. Potentially grapple many smaller foes at once.
Improved Grab (Ex): To use this ability, a tendriculos must hit a creature at least one size smaller than itself with its bite attack. It can then attempt to start a grapple as a free action without provoking an attack of opportunity. If it wins the grapple check, it establishes a hold and can try to swallow the opponent in the following round. A tendriculos can also use its improved grab ability on a tendril attack. If it wins the grapple check, it establishes a hold, picks up the opponent, and transfers it to the mouth as a free action, automatically dealing bite damage.
Also, for advancing improved grab, in Savage Species there are these two feats:
MULTIGRAB [MONSTROUS]
You can grapple enemies more firmly than normal with your natural attacks.
Prerequisite: Str 17, improved grab.
Benefit: When grappling an opponent with the part of your body that made the attack, you take only a -10 penalty on grapple checks to maintain the hold.
Normal: Without this feat, you take a -20 penalty on grapple checks to maintain a hold with the part of your body used to make the attack.
GREATER MULTIGRAB [MONSTROUS]
You can grapple enemies effortlessly with your natural weapons.
Prerequisite: Str 19, Dex 15, improved grab, Multigrab.
Benefit: When grappling an opponent with only part of your body that made the attack, you take no penalty on grapple checks to maintain the hold.
Normal: Without this feat, you take a -20 penalty (or a -10 penalty with Multigrab) on grapple checks to maintain a hold with only the part of your body used to make the attack.
Even if successive attacks with the holding body part don't work, you can grapple with as many different parts as you can attack with. Bite, claw, claw, tail, etc.
Maybe something I mentioned is what you are looking for
Enjoy.
Tyrol
