Grappling

[Really need to stop posting untested houserules, but I keep getting ideas from the blogosphere.]

This is meant for mass of goblins swarming and brigining down Sir ThinksHe'sAwesome and maybe for grabby monsters like crabs and octoterrapuses (land octopie).  Not for ju-jitsu, wresting, or other mostly mano-a-mano unarmed combat.  I'd just use normal combat for that.  When hit points gone you got a knee-lock or whatever.


Goals

• The strong man throws off buch of piled on grapplers trope.
• Different than regular combat, specifically freaking avoid non-leathal damage/hitpoints.
• Make weak, low level creatures a threat when swarming.
• Fit in with 1 attack roll, multiple damage dice, all attacks do d6 themes of my other house rules.
• Simple / vague enough to allow on the spot rulings for unusual situations. 
• Grappling is not effective when target has something sharp to poke you with.  That is until there are enough attackers target can't poke them all fast enough.

Grappling

2x the normal number of attackers may grapple a target.

Ungrappled defender (with weapon in hand/natural damage) negates up to BAB grapplers.  If all grapplers negated there is no grapple, attackers are kept at bay (and wasted their action looking for opening).  Alternatively grapplers can force their way through but then defender gets automatic 1 damage die vs each (up to BAB targets). 

All attackers combine into one to-grapple attack.  Attack roll gets +1 per attacker.  If attackers are "natural" or "trained" grapplers also add (avg/highest/lowest) to-hit bonus to attack roll.  Attackers must roll to-grapple every round.

On successful hit all grapplers add their grapple damage dice rolls to Pin Total.  If they choose to attempt to break free, a grappled defender auto-hits and subtracts their grapple damage dice roll from Pin Total. 

If, at end of round, Pin Total is:
  <= 0 defender is free/ungrappeld, pin total reset
  > 0 defender is grappled (restricted movement/actions(no normal attack))
  > defender's Str score, defender is held fast/pinned (no further grappling rolls, no actions. The defender has "lost".)




Grapple Damage Dice:
Is based on size but some creatures (crabs, boa constrictor) may have fixed amount.  Tiny 1pt, Small 1d4, Man-sized 1d6, Large 2d6, Huge 4d6, etc.
  Extra dice (1 per Str mod) are only given to defender.    Ex. a Str 18 man gets 4d6.



Aiding Grappled Defender: 
Depending on size of "pile" one can shoot/whack attackers without much danger of hurting defender.  Alternatively ally can "dive in" and subtract the roll of their  grapple damage dice from defender's Pin Total.  No to-hit required.


BAB:
Base Attack/to-hit Bonus what they get for class/level not including magic, buffs, stats mods, etc.